11 Jan 2021

02:30 PM

02:30 PM

As a global society we have been burning fossil fuels to meet our energy and transportation needs since the start of the industrial revolution. This has resulted in atmospheric CO2 concentrations much greater than at any other time during the last 650,000 years. That concentration reached a record 415 parts per million in May 2019. The replacement of fossil fuels with renewables, advances in energy efficiency, and carbon capture and storage are among the key strategies required to prevent warming beyond 2°C within this century. But they will not be enough. We need to ramp up our efforts in reducing CO2 emissions, and then we need to do even more. The Earth’s natural systems, such as forests and oceans, are capable of removing roughly half of global CO2 emissions each year, while the rest steadily accumulates in the atmosphere. Until now, our best approach to avoiding the worst impacts of climate change was simply to avoid such emissions in the first place. But because of our failure to act quickly and at a large enough scale, we are now faced with the need to go beyond that strategy—to actually start removing CO2 directly from the air. Trees and oceans already do this, but these systems are overwhelmed. Manufactured or synthetic removal systems are designed to pull CO2 from the atmosphere, and at a much faster rate than natural systems. This talk will review both the promise and pitfalls of this approach.

VIRTUAL

18 Jan 2021

04:30 PM

04:30 PM

Measurements in quantum physics, unlike their classical physics counterparts, can fundamentally yield discrete and random results. Historically, Niels Bohr was the first to hypothesize that quantum jumps occurred between two discrete energy levels of an atom. Experimentally, quantum jumps were directly observed many decades later in an atomic ion driven by a weak deterministic force under strong continuous energy measurement. The times at which the discontinuous jump transitions occur are reputed to be fundamentally unpredictable. Despite the non-deterministic character of quantum physics, is it possible to know if a quantum jump is about to occur? Our work1 provides a positive answer to this question: we experimentally show that the jump from the ground state to an excited state of a superconducting artificial three-level atom can be tracked as it follows a predictable “flight” by monitoring the population of an auxiliary energy level coupled to the ground state. The experimental results demonstrate that the evolution of the jump — once completed — is continuous, coherent, and deterministic. Based on these insights and aided by real-time monitoring and feedback, we then pinpoint and reverse one such quantum jump “mid-flight”, thus deterministically preventing its completion. Our findings, which agree with theoretical predictions essentially without adjustable parameters, lend support to the modern formulation of quantum trajectory theory; most importantly, they may provide new ground for the exploration of real-time intervention techniques in the control of quantum systems, such as the early detection of error syndromes. 1. Z. Minev et al., Nature 570, 200–204 (2019)

VIRTUAL

01 Mar 2021

04:30 PM

04:30 PM

Thousands of exoplanets are known to orbit nearby stars and small rocky planets are established to be common. Driving the field is the study of exoplanet atmospheres, with the goal of detecting a gas that might be indicative of life. A suitable “biosignature gas” is not just one that might be produced by life, but one that: can accumulate in an atmosphere against atmospheric radicals and other sinks; has strong atmospheric spectral features; and has limited abiological false positives. Which gases might be potential biosignature gases in an as yet unknown range of exoplanetary environments? New computer simulations and next-generation telescopes coming online means the ambitious goal of searching for “biosignature gases” in a rocky exoplanet atmosphere is within reach.

VIRTUAL

08 Mar 2021

04:30 PM

04:30 PM

Tensor network methods have become workhorses in the study of strongly correlated systems in condensed matter physics and increasingly also in the context of molecular systems. While their variational character provides results of remarkable accuracy, the capture quantum states featuring low entanglement well, a set of states often referred to as the 'physical corner'. While this physical describes ground states of local Hamiltonian problems from the condensed matter context well, the same cannot be said for problems involving molecules in quantum chemistry or systems undergoing time evolution. In this talk I will provide an overview over tensor network methods augmented by fermionic mode transformations in the context of molecular problems [1], condensed-matter simulations [2], and time evolution [3]. If time allows, I might briefly mention two new applications of tensor networks in being a design principle for building quantum devices [4] and in machine learning [5,6]. [1] Fermionic orbital optimisation in tensor network states (C. Krumnow, L. Veis, Ö. Legeza, J. Eisert, Phys. Rev. Lett. 117, 210402 (2016)) [2] Towards overcoming the entanglement barrier when simulating long-time evolution (C. Krumnow, J. Eisert, Ö. Legeza, arXiv:1904.11999) [3] Dimension reduction with mode transformations: Simulating two-dimensional fermionic condensed matter systems (C. Krumnow, L. Veis, J. Eisert, Ö. Legeza, arXiv:1906.00205) [4] Simulating topological tensor networks with Majorana qubits (C. Wille, R. Egger, J. Eisert, A. Altland, Phys. Rev. B 99, 115117 (2019)) [5] Expressive power of tensor-network factorizations for probabilistic modeling, with applications from hidden Markov models to quantum machine learning, I. Glasser, R. Sweke, N. Pancotti, J. Eisert, J. I. Cirac, arXiv:1907.03741, NeurIPS (2019)) [6] Tensor network approaches for learning non-linear dynamical laws (A. Goessmann, M. Goette, I. Roth, G. Kutyniok, J. Eisert, R. Sweke, Submitted to ICML2020 (2020))

VIRTUAL

29 Mar 2021

04:30 PM

04:30 PM

In standard text books on electrodynamics, Maxwell's laws are often illustrated using field lines -- a notion that lacks relativistic covariance and obscures the superposition principle (see e.g. R. Feynman in: The Feynman Lectures on Physics, Vol II, Chapter 1-5). In this colloquium, an improved variant of the field line picture is presented: the discrete approximation of the electromagnetic field by chains (B and D are modeled as 1-chains, E and H as 2-chains). The language of chains offers a simple, direct and intuitive approach to Maxwell's electrodynamics, without compromising physical or mathematical correctness. Fundamental aspects such as parity invariance or the transcription of the theory to curved space-time are especially transparent in this approach. The talk illustrates the chain picture at a number of examples including vortex motion in superconductors, spin-orbit coupling, equivalence between problems of magneto- and electrostatics, emission of an electromagnetic signal by the discharge of a capacitor, quantum Hall-Ohm law. The colloquium is an outgrowth of the speaker's 30 years of experience teaching electrodynamics to physics students.

VIRTUAL

19 Apr 2021

04:30 PM

04:30 PM

Superconductivity comes in a wide variety of incarnations including conventional s-wave, high-Tc d-wave, and topological p-wave. While these states are well defined theoretically, they are extremely difficult to distinguish experimentally: all superconductors have Cooper pairs, a Meissner effect, and a zero-resistance state, while any differences between states are subtle. I will give an overview of the experimental situation with a particular focus on how to find a bulk, three-dimensional topological superconductor, drawing on my own group's research on Sr2RuO4 and UTe2.

VIRTUAL

03 May 2021

04:30 PM

04:30 PM

In 2019, Google researchers carried out an experiment where they achieved "quantum supremacy". This is defined as when a quantum computer performs *any* task in a way that a classical computer takes impractical amounts of time to simulate its outcome. This is a huge milestone for the field, but several milestones lie ahead. In this talk, I will describe a potential algorithmic road to "quantum advantage", ie. the moment when a quantum computer carries out a *practical* task on a system that is unreachable by current classical computers. To reach quantum advantage presumably many years of hardware development and algorithmic development lie ahead of us. The current era of quantum computing, coined near-term intermediate-scale quantum computing (NISQ) by John Preskill presents many challenges and opportunities. I will discuss this algorithmic road in the context of algorithms for the simulation of molecules and materials, as well as will briefly mention quantum machine learning applications.

VIRTUAL

07 Jun 2021

04:30 PM

04:30 PM

Will a large economy be stable? Building on Sir Robert May’s original argument for large ecosystems, we conjecture that evolutionary and behavioural forces conspire to drive the economy towards marginal stability. We study networks of firms in which inputs for production are not easily substitutable, as in several real-world supply chains. We argue that such networks generically become dysfunctional when their size increases, when the heterogeneity between firms becomes too strong, or when substitutability of their production inputs is reduced. At marginal stability and for large heterogeneities, we find that the distribution of firm sizes develops a power-law tail, as observed empirically. Crises can be triggered by small idiosyncratic shocks, which lead to “avalanches” of defaults characterized by a power-law distribution of total output losses. This scenario would naturally explain the well-known “small shocks, large business cycles” puzzle, as anticipated long ago by Bak, Chen, Scheinkman, and Woodford.

VIRTUAL

28 Jun 2021

04:30 PM

04:30 PM

Two-dimensional electron gases under a strong magnetic field have tremendously expanded our understanding of many-body physics, with the discovery of integer and fractional quantum Hall effects, together with chiral edge states, fractional excitations, anyons. Another striking effect is the strong coupling between charge and spin/valley degrees of freedom, which takes place near integer filling of the magnetic Landau levels. More precisely, because of the large energy gap associated to cyclotron motion, any slow spatial variation of the spin background induces a variation of the electronic density proportional to the topological density of the spin background. Minimizing Coulomb energy leads to an exotic class of two-dimensional crystals, which exhibit a periodic non-collinear spin texture called a Skyrmion lattice. I will review the history of these concepts, with an emphasis on the notions of Berry phases and Berry curvature, which play a prominent role in all aspects of topological condensed matter physics. A main feature of these Skyrmion crystals is that their theoretical description involves effective theories with local and possibly non-Abelian gauge symmetries. It is therefore a theoretical challenge to identify the actual physical degrees of freedom in such systems. I will show how this may be achieved using some ideas from complex geometry. The main outcome of such analysis is the existence of two regimes depending on whether the topological charge per unit cell is smaller (unfrustrated case) or larger (frustrated case) than the number of internal states (spin/valley) accessible to electrons.

Seminarroom 4

05 Jul 2021

04:30 PM

04:30 PM

We discuss recent theoretical progress in understanding the nature of yielding in amorphous materials. Within an athermal elastoplastic model in quasistatic shear, we find that yielding is brittle in the limit of large system size, whatever the level of annealing/ageing of the sample prior to shear. For small systems, in contrast, we find a crossover from apparently ductile to brittle yielding behaviour with increasing degree of sample annealing prior to shear. Differences between studies in one and two spatial dimensions will be discussed. We will also compare the nature of ductile/brittle yielding in athermal materials with that in thermal materials.

VIRTUAL

06 Jul 2021

04:40 PM

04:40 PM

Cells and tissues are highly dynamic but at the same time need to withstand large mechanical loads. This paradoxical mechanical behavior is governed by fibrous protein scaffolds known as the cytoskeleton and the extracellular matrix. Fibrous networks have many advantageous mechanical properties: fibers can form space-filling elastic networks at low volume fractions and they reversibly stress-stiffen, which provides protection from damage. However, it is still poorly understood how biopolymer networks can combine these features with the ability to dynamically adapt their structure and mechanics. This question has guided our research over the past years. I will provide an overview of the most important things we have learned by performing quantitative measurements on reconstituted cytoskeletal and extracellular matrix networks. We perform these measurements from the macroscopic scale (using rheology) all the way down to the molecular scale (using optical tweezers, in situ small-angle-X-ray scattering, and atomic force microscopy). I will furthermore mention connections to applications in bottom-up synthetic biology and for tissue (re)generation.

VIRTUAL

19 Jul 2021

04:30 PM

04:30 PM

Particle colliders are our main laboratory tool to study the smallest distance scales accessible to humankind. Recent years have seen major advances, notably the discovery of long-hypothesised, but qualitatively new interactions in the Higgs sector, which are essential for a universe as we know it. Central to the progress of collider particle physics is our understanding of the strong interaction and its theoretical formulation, quantum chromodynamics. This rich theory operates across many orders of magnitude in distance and momentum, producing hundreds of particles in each collision. One of today's major challenges is to learn how to maximally and reliably exploit the resulting information.

VIRTUAL

20 Jan 2020

04:30 PM

04:30 PM

I'll present the hydrodynamic theory of ``Malthusian Flocks": moving aggregates of self-propelled entities (e.g., organisms, cytoskeletal actin, microtubules in mitotic spindles) that reproduce and die. Long-ranged order (i.e., the existence of a non-zero average velocity $\langle \bf{v} (\bf{r,t}) \rangle \neq \bf{0}$) is possible in these systems, even in spatial dimension $d=2$. Their spatiotemporal scaling structure can be determined exactly in $d=2$; furthermore, they lack both the longitudinal sound waves and the giant number fluctuations found in immortal flocks. Number fluctuations are very ${\it persistent}$, and propagate along the direction of flock motion, but at a different speed. I'll also present recent results for the three dimensional version of this problem, which required the first full blown dynamical renormalization treatment of a flocking system in its ordered phase.

Seminarroom 1+2+3

27 Jan 2020

04:30 PM

04:30 PM

Causal Dynamical Triangulations (CDT) is a candidate theory for quantum gravity, formulated nonperturbatively as the scaling limit of a lattice theory in terms of piecewise flat (triangulated) spacetimes. From a technical and conceptual perspective, an important feature of this approach is its elegant resolution of the problem of how to treat the diffeomorphism symmetry of the classical theory in the full, background-free quantum theory. This has enabled the concrete computation of geometric observables in a highly nonperturbative, Planckian regime, an important step in putting quantum gravity on a quantitative footing, and understanding the structure of quantum spacetime. While the need to find quantum observables describing this regime is common to all approaches, CDT quantum gravity provides a concrete testing ground for implementation and measurements. In particular, a new notion of quantum Ricci curvature has opened a new window on some of the counterintuitive properties of quantum geometry.

Seminarroom 1+2

03 Feb 2020

04:30 PM

04:30 PM

The set of compounds (Ca/Sr)$_2$RuO$_4$ exhibit a rich array of properties, ranging from fermi liquid/Hunds metal physics and nontrivial superconductivity to metal-insulator transition that is driven by the interplay of correlated electron and lattice physics and is highly controllable by strain and current. Following a brief review of the material family, this talk will focus on the end-member Ca$_2$RuO$_4$, showing how attempts to understand the properties via multiple theoretical methods are leading to new insights into the techniques of many-body physics, how the metal insulator transition has provided new insights into the role of the lattice in correlated electron physics, and how the current-driven transition is providing new insights into nonequilibrium properties of correlated systems.

Seminarroom 1+2

17 Feb 2020

04:30 PM

04:30 PM

Connecting theoretical models for exotic quantum states to real physical systems is a key goal in the study of quantum materials. Among such theoretical models, a “toy model” is one made deliberately simplistic in order to demonstrate new physical concepts and their underlying mechanisms. Such models have proven to be tremendously successful in offering insight in to new condensed matter phenomena including those involving electronic topology and correlation. We describe here our recent progress in experimentally realizing “toy model” quantum materials which, in analogy to their theoretical counterparts, are designed to capture simple model systems by lattice and superlattice design. We detail developments in synthesizing and studying magnetic and superconducting materials that allow for new connections to long-standing predictions for unusual topological electronic phases. We close with a perspective for realizing further toy model systems in complex material structures.

Seminarroom 1+2

02 Mar 2020

04:30 PM

04:30 PM

Organisms are subject to the laws of physics, so the process of evolution is constrained by these fundamental laws. Classic and recent studies of the biophysical limits facing organisms have shown how fundamental physical constraints can be used to predict broad-scale relationships between body size and organismal biomechanics and physiology. In this talk I will provide a broad framework for the connection between physical constraints, evolution, and allometric physiology. I will focus on an under-appreciated aspect of allometry: ultimate limits that occur at distinct scales for broad categories of organisms. I will connect these limits to higher-order evolutionary phenomena such as major evolutionary transitions and constraints on populations of organisms. In discussing these concepts I will cover case-studies ranging from bacterial physiology to mammalian population dynamics, and I will outline a broad physics-based evolutionary theory.

Seminarroom 1+2

08 Jun 2020

04:30 PM

04:30 PM

Artificial Intelligence is about to have a dramatic impact on many sectors of human activity. In the last ten years, thanks to the development of machine learning in “deep networks”, we have experienced spectacular breakthroughs in diverse applications such as automatic interpretation of images, speech recognition, consumer profiling, or go and chess playing. Algorithms are now competing with the best professionals at analyzing skin cancer symptoms or detecting specific anomalies in radiology; and much more is to come. Worrisome perspectives are frequently raised, from massive job destruction to autonomous decision-making “warrior” robots. In this talk, we shall open the black box of deep networks and explore how they are programmed to learn from data by themselves, using a statistical physics perspective. This will allow us to understand their limits, to underline the lack of theoretical understanding, to question whether their achievements have anything to do with “intelligence”, and to reflect on the foundations of scientific intelligence.

VIRTUAL

15 Jun 2020

04:30 PM

04:30 PM

The data science revolution is finally enabling the development of large-scale data-driven models that provide scenarios, forecasts and risk analysis for infectious disease threats. These models also provide rationales and quantitative analysis to support policy making decisions and intervention plans. At the same time, the non-incremental advance of the field presents a broad range challenges: algorithmic (multiscale constitutive equations, scalability, parallelization), real time integration of novel digital data stream (social networks, participatory platform, human mobility etc.). I will review and discuss recent results and challenges in the area, and focus on ongoing work aimed at responding to the COVID-19 pandemic.

VIRTUAL

10 Aug 2020

04:30 PM

04:30 PM

Thermodynamics provides a robust conceptual framework and set of laws that govern the exchange of energy and matter. Although these laws were originally articulated for macroscopic objects, nanoscale systems also exhibit “thermodynamic¬-like” behavior – for instance, biomolecular motors convert chemical fuel into mechanical work, and single molecules exhibit hysteresis when manipulated using optical tweezers. To what extent can the laws of thermodynamics be scaled down to apply to individual microscopic systems, and what new features emerge at the nanoscale? I will describe some of the challenges and recent progress – both theoretical and experimental – associated with addressing these questions. Along the way, my talk will touch on non-equilibrium fluctuations, “violations” of the second law, the thermodynamic arrow of time, nanoscale feedback control, strong system-environment coupling, and quantum thermodynamics.

VIRTUAL

07 Sep 2020

04:30 PM

04:30 PM

Non-equilibrium quantum many-body systems can display fascinating phenomena relevant for various fields in science ranging from physics, to chemistry, and ultimately, for the broadest possible scope, life itself. The challenge with these systems, however, is that the powerful formalism of statistical physics, which have allowed a classification of quantum phases of matter at equilibrium does not apply. Therefore, using controllable cold atomic systems to shed light on the organizing principles and universal behaviors of dynamical quantum matter is highly appealing. One emerging paradigm is the dynamical phase transition (DPT) characterized by the existence of a long-time-average order parameter that distinguishes two non-equilibrium phases. I will report the observation of a DPT in two different but complementary systems: a trapped quantum degenerate Fermi gas and long lived arrays of atoms in an optical cavity. I will show how these systems can be used to simulate iconic models of quantum magnetism with tunable parameters and to probe the dependence of their associated dynamical phases on a broad parameter space. Besides advancing quantum simulation our studies pave the ground for the generation of metrologically useful entangled states which can enable real metrological gains via quantum enhancement.

VIRTUAL

14 Sep 2020

04:30 PM

04:30 PM

Metamaterials are rationally designed three-dimensional composites made of one or more bulk ingredient materials allowing for effective-medium properties going beyond (“meta”) those of the ingredient materials, qualitatively and/or quantitatively. In this talk, I focus on three-dimensional crystalline metamaterials. After an introduction into the concept, I discuss recent examples. This includes artificial cubic chainmail-like crystals leading to a sign reversal of the effective isotropic Hall coefficient, anisotropic crystals exhibiting the parallel Hall effect, chiral cubic crystals showing twist effects and acoustical activity forbidden in Cauchy elasticity, and cubic crystals exhibiting a sign reversal of the isotropic thermal expansion coefficient and a negative static effective compressibility, respectively.

VIRTUAL

21 Sep 2020

04:30 PM

04:30 PM

Transport is the defining property of states of matter, but often the most difficult to understand. Strongly interacting Fermi gases are especially challenging, despite their ubiquitous presence across many fields of physics, from atomic nuclei to high-temperature superconductors and neutron stars. Experiments on ultracold fermionic atoms allow the direct measurement of transport properties in ideal model systems where the Hamiltonian is precisely known, while transport properties are difficult to calculate theoretically. In this talk I will present our experiments on two systems: The unitary Fermi gas, where interactions are tuned to be as strong as quantum mechanics allows, and the Fermi-Hubbard lattice gas, believed to hold the key for our understanding of high-temperature superconductivity. Locally resolved sound and heat transport can distinguish superfluid and normal flow regimes in the unitary gas. Our observation of spin transport in the Fermi-Hubbard system reveals the mechanism governing quantum magnetism.

VIRTUAL

28 Sep 2020

04:30 PM

04:30 PM

Deep learning is very powerful at a variety of tasks, including self-driving cars and playing go beyond human level. Despite these engineering successes, why deep learning works remains unclear; a question with many facets. I will discuss two of them: (i) Deep learning is a fitting procedure, achieved by defining a loss function which is high when data are poorly fitted. Learning corresponds to a descent in the loss landscape. Why isn’t it stuck in bad local minima, as occurs when cooling glassy systems in physics? What is the geometry of the loss landscape? (ii) in recent years it has been realised that deep learning works best in the over-parametrised regime, where the number of fitting parameters is much larger than the number of data to be fitted, contrarily to intuition and to usual views in statistics. I will propose a resolution of these two problems, based on both an analogy with the energy landscape of repulsive particles and an analysis of asymptotically wide nets.

VIRTUAL

19 Oct 2020

04:30 PM

04:30 PM

A Josephson junction in a topological superconductor can inject a charge e/2 into a normal-metal contact, carried by chiral Majorana edge modes. We address the question whether this half-integer charge is a sharp observable, without quantum fluctuations. Because the Majorana modes are gapless, they support charge fluctuations in equilibrium at zero temperature. But we find that the excess noise introduced out of equilibrium by the e/2 charge transfer vanishes. We discuss a strategy to reduce the equilibrium fluctuations, by means of a heavy-tailed time-dependent detection efficiency, to achieve a nearly noiseless half-integer charge transfer.

VIRTUAL

23 Nov 2020

04:30 PM

04:30 PM

Entangled photons have become an essential workhorse for experiments on the foundations of quantum mechanics. Tests of Bell’s Inequality (cf. the Einstein-Podolsky-Rosen Paradox) have with increasing sophistication ruled out more and more alternative views to quantum mechanics. Besides that, they emerged to be also essential for a number of future quantum communication tasks. In most experiments, entanglement of two qubits, that is, of two photons in two states, e.f. polarization are employed. Going beyond two particles, and beyond two dimensions interesting novel phenomena arise. One of them is the GHZ contradiction, where a conflict between an objective local (i.e. classical) view in quantum mechanics arises even for non-statistical predictions of the theory. A most fascinating subject is entanglement swapping, where photons can be entangled which share no common past. In delayed-choice entanglement swapping, the decision whether two photons are entangled or not can be done at a time after they have already been detected and their measurement results (e.g. their polarization) has been registered. Going beyond qubits, states of orbital angular momentum (OAM) of photons provide an in principle unlimited discrete state space where the photons can also be entangled in many different ways. That way, entanglement has been confirmed for quantum numbers above 10.000 and between two photons, each carrying more than 100-dimensional states. A Cosmic Bell Test employed very distant quasars. Also, quantum communication was established between Europe and China using the Chinese satellite Micius. I will conclude with the Big Bell Test, an experiment to test quantum entanglement employing human free will with twelve laboratories on five continents and a hundred million human participants.

VIRTUAL

14 Dec 2020

01:30 PM

01:30 PM

Quantum Chromodynamics (QCD) is the fundamental theory for elementary particles (quarks and gluons) which constitutes the proton, the neutron and the atomic nuclei. Because the quarks and gluons are strongly interacting, their arise characteristic phases at finite temperature and baryon density: The hadronic phase at low temperature and density with the non-perturbative phenomena such as confinement and chiral symmetry breaking, the quark-gluon plasma phase at high temperature and low density, and the superconducting quark matter at low temperature and high density. In this colloquium, I discuss the characteristic properties of these phases on the basis of the many-body approach to QCD as well as their relevance to the physics of early universe, accelerator experiments, neutron stars and gravitational waves.

VIRTUAL

21 Jan 2019

04:30 PM

04:30 PM

Symmetry and topology are two of the conceptual pillars that underlie our understanding of matter. While both ideas are old, over the past several years a new appreciation of their interplay has led to dramatic progress in our understanding of topological electronic phases. A paradigm that has emerged is that insulating electronic states with an energy gap fall into distinct topological classes. Interfaces between different topological phases exhibit gapless conducting states that are protected and are impossible to get rid of. In this talk we will discuss the application of this idea to the quantum Hall effect, topological insulators, topological semimetals and topological superconductors. The latter case has led to the quest for observing Majorana fermions in condensed matter, which opens the door to proposals for topological quantum computation. We will close by surveying the frontier of topological phases in the presence of strong interactions.

Seminarroom 1+2

04 Feb 2019

04:30 PM

04:30 PM

When confining photons in semiconductor lattices, it is possible deeply modifying their physical properties. Photons can behave as finite or even infinite mass particles, photons inherit topological properties and propagate along edge states without back scattering, photons can become superfluid and behave as interacting particles. These are just a few examples of properties that can be imprinted into fluids of light in semiconductor lattices. Such manipulation of light present not only potential for applications in photonics, but great promise for fundamental studies. During the talk, I will illustrate the variety of physical systems we can emulate with fluids of light by presenting a few recent experiments: a photonic benzene molecule that emits helical photons, a photonic 1D lattice with topological edge states and photonic graphene with exotic Dirac cones. Perspectives in terms of quantum simulation will be discussed.

Seminarroom 1+2

18 Feb 2019

04:30 PM

04:30 PM

The idea that many body systems in complex materials may self-organize under highly non-equilibrium conditions suggests that entirely new emergent states with new and unexpected functionalities might be created in this way. The route for creation of such states is not limited to symmetry-breaking phase transitions, and entirely novel mechanisms may come into play. I will discuss recent experimental findings of mesoscopically textured topologically protected metastable states created through density-driven non-equilibrium transitions. Combining ultrafast optical pulse excitation with scanning tunneling microscopy under various non-equilibrium conditions we find various intertwined electronic orders and metastable amorphous electronic states stabilized in real space by non-trivial topological defects. The relaxation of these states reveals a novel state of configurational quantum electronic matter that may find its uses in ultrafast memory devices.

Seminarroom 1+2

25 Feb 2019

04:30 PM

04:30 PM

Superconducting qubits are an attractive platform for quantum computing since they have demonstrated high-fidelity quantum gates and extensibility to modest system sizes. Nonetheless, an outstanding challenge is stabilizing their energy-relaxation times, which can fluctuate unpredictably in frequency and time. Here, we use qubits as spectral and temporal probes of individual two-level-system defects to provide direct evidence that they are responsible for the largest fluctuations. This research lays the foundation for stabilizing qubit performance through calibration, design, and fabrication.

Seminarroom 1+2

11 Mar 2019

04:30 PM

04:30 PM

The recent development of topological insulator states for photons1–3 has led to an exciting new field of “topological photonics,” which has as a central goal the development of extremely robust photonic devices4. Topological insulator physics has been studied extensively in condensed matter5 and cold atoms6. However, photonic systems offer the possibility of non-Hermitian effects through the engineering of optical gain and loss, which opens an entire new field of physics. In this talk, we will discuss our recent experimental work on non-Hermitian topological phenomena in coupled lattice systems, in particular the first demonstration of non-hermitian PT-symmetric topological interface state. References [1] Haldane, F. D. M. & Raghu, S., Phys. Rev. Lett. 100, 013904 (2008) [2] Wang, Z. et al., Nature 461, 772–775 (2009) [3] Rechtsman, M. C. et al., Nature 496, 196–200 (2013) [4] Hafezi et al., Nature Physics 7, 907-912 (2011) [5] Hasan, M. Z. & Kane, C. L., Rev. Mod. Phys. 82, 3045–3067 (2010) [6] Jotzu, G. et al., Nature 515, 237–240 (2014)

Seminarroom 1+2

08 Apr 2019

04:30 PM

04:30 PM

Impurity engineered states are the key component of modern electronics. We expect impurity engineered states will continue to be an important ingredient in quantum technologies beyond Si. New platforms that take advantage of impurity engineered bands such as superconductors and Dirac Materials are emerging. In this talk I will review the status and future perspectives of the field of impurity bound states in superconductors and will discuss striking similarities and important differences between defect states in superconductors and Dirac materials. I will highlight the recent progress made in our understanding of Yu-Shiba-Rusinov states in superconductors and topological states and illustrate the proposed induction of novel odd frequency Berezinskii pairing by YSR impurities. I will also discuss the universal nature of impurity resonances in unconventional SC and Dirac Materials and the implications these resonances have on functional properties of doped Dirac materials. Work supported by ERC, KAW and Villum Center for Dirac Materials.

Seminarroom 1+2

29 Apr 2019

04:30 PM

04:30 PM

The mechanics of cells and tissues are largely governed by scaffolds of filamentous proteins that make up the cytoskeleton, as well as extracellular matrices. Evidence is emerging that such networks can exhibit rich mechanical phase behavior. A classic example of a mechanical phase transition was identified by Maxwell for macroscopic engineering structures: networks of struts or springs exhibit a continuous, second-order phase transition at the isostatic point, where the number of constraints imposed by connectivity just equals the number of mechanical degrees of freedom. We will present recent theoretical predictions and experimental evidence for mechanical phase transitions in both synthetic and biopolymer networks. Living systems typically operate far from thermodynamic equilibrium, which affects both their dynamics and mechanical response. As a result of enzymatic activity at the molecular scale, living systems characteristically violate detailed balance, a fundamental principle of equilibrium statistical mechanics. We discuss fundamental non-equilibrium signatures of living systems, including violations of detailed balance at the meso-scale of whole cells.

Seminarroom 1+2

06 May 2019

04:30 PM

04:30 PM

I discuss the interplay between non-Fermi liquid behavior and superconductivity near a quantum-critical point (QCP) in a metal. It is widely thought that the tendency towards superconductivity and towards non-Fermi liquid behavior compete with each other, and if the pairing interaction is reduced below a certain threshold, the system displays a naked non-Fermi liquid QC behavior. I show that the situation is more complex. First, there is a difference between spin-triple and spin-singlet superconductivity. For spin-triplet pairing, thermal fluctuations are crucial and make superconducting transition first order. For spin-singlet pairing, they are essentially irrelevant, and the transition is second order. Second, I show that for spin-singlet pairing, there are multiple solutions with the same gap symmetry. For all solutions, except one, Tc vanishes when the pairing interaction drops below the threshold. For the one special solution, Tc remains finite even when the pairing interaction is arbitrary small, despite that there is no Cooper logarithm. I argue that superconductivity between this Tc and a lower T, when other solutions appear, is special, as it is entirely induced by fermions with the first Matsubara frequency. I show that this has specific implications for the observable quantities, such as the density of states and the spectral function.

Seminarroom 1+2+3

13 May 2019

04:30 PM

04:30 PM

Two dimensional materials provide new avenues for synthesizing compound quantum systems. Monolayers with vastly different electric, magnetic or optical properties can be combined in van der Waals heterostructures which ensure the emergence of new functionalities; arguably, the most spectacular example to date is the observation of strong correlations and low electron density superconductivity in Moire superlattices obtained by stacking two monolayers with a finite twist angle. Optically active monolayers such as molybdenum diselenide provide a different "twist" as they allow for investigation of nonequilibrium dynamics in van der Waals heterostructures by means of femtosecond pump-probe measurements. Moreover, interactions between electrons and the elementary optical excitations such as excitons or polaritons, provide an ideal platform for investigation of quantum impurity physics, with possibilities to probe both Fermi- and Bose-polaron physics as well as mixtures with tunable density of degenerate fermions and bosons. After introducing the framework we use to describe many-body optical excitations in van der Waals heterostructures, I will describe two recent developments in the field. The first experiment uses pump-probe measurements to demonstrate how exciton-electron interactions beyond the non-self-consistent T-matrix approximation lead to optical gain by stimulated cooling of exciton-polaron-polaritons. The second experiment shows that a tri-layer system, consisting of two semiconducting monolayers separated by an insulating layer, could lead to hybridization of intra- and inter-layer excitons. The latter has potential applications ranging from strongly interacting polaritons to reaching Feshbach resonance condition in exciton-electron scattering.

Seminarroom 1+2

20 May 2019

04:30 PM

04:30 PM

The elastic properties of materials are determined by a few material constants such as the Young’s modulus. Using super-structures one can effectively change these “constants”. In this way we obtain functionalities such as wave-guiding, acoustic lensing or programmable failure. I will show how topological band theory, known from the description of electrons in solids, provides us with a powerful design-principle for such mechanical metamaterials. Moreover, mechanical metamaterials offer a powerful platform for the study of fundamentally new phenomena that are hard to observe in other arenas. Here, I will highlight the first measurement of a quadrupole topological insulator in a silicon based metamaterial and the implementation of an axial gauge field in an acoustic Weyl system.

Seminarroom 1+2

27 May 2019

04:30 PM

04:30 PM

In this talk I introduce a phenomenon of enhancement of quantum memory storage capacity that is taking place in a wide class of systems with high occupancy of cold bosons at criticality. The S-matrix formulation shows that black holes are prominent members of this category. From particle physicists perspective a black hole is describable as a critical state of maximal memory storage capacity of soft gravitons at an extremely high occupation number. The same is true about a de Sitter type Universe. Both systems carry a maximal amount of quantum information that is protected against the standard semi-classical evolution. This leads to some important consequences. In particular, the primordial quantum memory pattern carried by the de Sitter Hubble patch from which our Universe evolved as a result of cosmic inflation was not erased by the latter process and is of observational importance. This opens up a conceptually new opportunity of catching the glimpses of the Universes's primordial quantum hair. The universal nature of the enhanced memory phenomenon allows to study and simulate black hole and de Sitter type quantum information storage and processing in laboratory systems with cold bosons.

Seminarroom 1+2

03 Jun 2019

04:30 PM

04:30 PM

Shape constrains and enables function across scales. But how can we design and control shape, i.e. solve the basic inverse problems in physical geometry. I will discuss our work in this area that focuses on 3 different paradigms: (i) using origami to fold flat sheets into curved surfaces, (ii) using kirigami to reshape planar domains and tile arbitrary surfaces, (iii) using biomimetic 3D and 4D printing combined with designer metrics that allow us to “grow” a flat surface into a complex 3D shape such as a flower or a face.

Seminarroom 1+2

17 Jun 2019

04:30 PM

04:30 PM

The description of open quantum systems is amenable to a broad range of theoretical tools. Those include the derivation of different types of reduced master equations from specific microscopic modes and under the validity of physically motivated assumptions. A conceptually different approach relies on the formulation of phenomenological master equations, which in the more abstract formalism yield to the description of open system dynamics in terms of quantum channels. Using quantum metrology as a thread, I will illustrate the interrelation and complementarity of different formalisms to describe open quantum systems in order to provide a comprehensive approach to determining fundamental limits to the ultimate achievable precision in metrology and sensing.

Seminarroom 1+2

24 Jun 2019

04:30 PM

04:30 PM

The study of structural colour in brightly coloured animals is an exciting interdisciplinary area of research. Complex photonic bandgap (PBG) structures that occur naturally cross a broad range of animals and plants, suggest broad innovation both in nature’s use of materials and in its manipulation of light and colour. In certain butterflies for instance, ultra-long-range visibility of up to one half-mile is attributed to photonic structures that are formed by discrete multilayers of cuticle and air. This contrasts, in other butterfly species, to photonic structures designed more for crypsis and which not only produce strong polarisation effects but can also create additive colour mixing using highly adapted periodicity. Optical systems also exist that employ remarkable 2D and 3D photonic crystals of cuticle to produce partial PBGs, with the effect that bright colour is reflected, or fluorescence emission is inhibited, over specific angle ranges. From the perspective of modern optical technology, these structures arguably indicate a significant functional advance, since in principle, such 2D and 3D periodicities are potentially able to manipulate the flow of light more completely. This presentation will offer an overview, for a more general audience, of this emerging field of study, as well as describing several of the exciting recent discoveries that reflect nature’s optical design ingenuity, and some technological applications to which they are currently being applied.

Seminarroom 1+2

01 Jul 2019

04:30 PM

04:30 PM

The experimental platform of atoms manipulated by light offers answers to a broad spectrum of open questions. With two explicit and very different examples I will give you a glimpse how broad this spectrum is. I will start with a fundamental question in oceanography: At what time has the deep water in the ocean been in exchange with the atmosphere? Quantum atom optics offers the experimental possibility to detect the very rare Argon 39 atoms one by one and with that allows the dating of water samples as small as ten liters [1]. A very different question in physics is about the existence of universal behavior. Specifically in respect to time dynamics this has only recently been discussed theoretically in the context of the early phase of a heavy ion collision. 'Universal' means in this context, that the evolution does not depend on the initial condition and follows the scaling hypothesis in time and space. I will introduce the concept and present the first observation of this phenomenon in highly controlled ultracold Bose gases [2]. [1] Ar-39 dating with small samples provides new key constraints on ocean ventilation, Nature Comm. 9, 5046 (2018). [2] Observation of universal dynamics in a spinor Bose gas far from equilibrium, Nature 563, 217 (2018).

Seminarroom 1+2

08 Jul 2019

04:30 PM

04:30 PM

Physicists have been thinking for a century about ordered solids. But ordered systems can’t compete with what biological systems such as proteins, which aren’t ordered, can do. We’ve discovered that relaxing the constraint of order increases design flexibility enormously, so that systems can be tuned to perform complex biologically-inspired tasks. Allostery in a protein is a phenomenon in which a molecule binding locally to one site affects the ability of another molecule to bind at a second distant site. Inspired by the long-range coupled conformational changes that constitute allosteric function in proteins, we tune in “allostery” into disordered mechanical networks derived from granular packings by modifying the network architecture to control the local strain at one point in such a network in response to a strain applied elsewhere in the system. In another biological example, the vascular network in the brain contracts and dilates blood vessels in order to direct enhanced blood flow to multiple specific regions of the brain as it performs multiple tasks at once. We have designed flow networks to accomplish similar complex tasks. In both examples, we address a key question: what, precisely, are we tuning into the structure in order to accomplish the function? Surprisingly, we find that the structure/function relationship is not geometrical, but topological in nature.

Seminarroom 1+2

15 Jul 2019

04:30 PM

04:30 PM

Topological spin textures in chiral magnets such as skyrmions attract great interest as a possible route towards spintronics devices. Central to the suitability for applications are the mechanisms controlling the long-term stability and decay processes. Starting from the spectrum of low-lying excitations the effects of kinetic arrest and supercooling will be compared with strongly driven non-equilibrium dynamics. These identify topological magnetic order far from equilibrium as an exciting approach for the exploration of the fundamentals of topological protection and in the search for dynamically stabilized electronic phases.

Seminarroom 1+2

22 Jul 2019

04:30 PM

04:30 PM

In 1676, using candle light for illumination and a small glass sphere as the lens, Antonie van Leeuwenhoek revealed to the world the beauty and complexity of a microscopic universe densely populated by living microorganisms. Today, using lasers, spatial light modulators, digital cameras and computers, we investigate the statistical and fluid mechanics of microswimmers in ways that were unimaginable only 50 years ago. With light we can image bacteria as they swim rapidly through 3D environments, apply gentle and controllable force fields or sculpt the 3D structure of their environment. In addition to shaping the physical world outside cells we can also use light to control the internal biological state of microorganisms that are genetically engineered to respond to light signals. I will review our recent work on the interactions between light, matter and bacteria, from the fundamental problems of rectification and non-equilibrium steady states in active matter to the use of genetically modified bacteria as propellers for micro-machines or as a "living" paint that can be controlled by light.

Seminarroom 1+2

29 Jul 2019

04:30 PM

04:30 PM

The pioneering work on geometrical frustration dates back to the 1920s, when Linus Pauling realized that the hydrogen bonds between H$_2$O molecules in ice can be allocated in multiple ways. A given oxygen atom in water ice is situated at the vertex of a diamond lattice and has four nearest-neighbor oxygen atoms, each connected via an intermediate proton according to the ice rule “two-in two-out”. Although these considerations used electric dipoles, Phil Anderson mapped them to a spin model possessing an extensive degeneracy of states. Quantum spin liquids attract great interest due to their exceptional magnetic properties characterized by the absence of long-range order down to low temperatures despite the strong magnetic interaction. Commonly these compounds are strongly correlated electrons systems, and their electrodynamic response is governed by the Mott gap in the excitation spectrum. Here we will summarize and discuss the optical properties of several two-dimensional quantum spin liquid candidates with different degrees of effective correlations. Placing organic molecules on a triangular lattice, a spin liquid ground state can be realized which allows us to investigate the genuine Mott state in the absence of magnetic order. Combining our optical data with pressure-dependent transport studies and theoretical calculations, we can construct a universal phase diagram of the correlation-controlled Mott insulator. But how important is the coupling of the fluctuating magnetic moments? How important is disorder for the electronic properties? If this resembles a quantum phase transition, is there a superconducting phase found in the vicinity and what is the superconducting glue? Can our findings be generalized, when going to a kagome or hexagonal lattice, realized in Herbert-smithites or $\alpha$-RuCl$_3$ for instance? Reference: A. Pustogow et al., Nature Materials 17, 773 (2018); Phys. Rev. Lett. 121, 056402 (2018). M. Dressel et al., J. Phys. Cond. Matter 30, 203001 (2018)

Seminarroom 1+2

05 Aug 2019

04:30 PM

04:30 PM

The established and highly successful description of metals is based on Landau’s Fermi liquid theory. The relevant phase space for electron-electron collisions is determined by the Pauli blocking of a degenerate Fermi gas due to its Fermi surface. In some strongly correlated systems narrow bands form and the energetics of the system at elevated energies or temperatures becomes dominated by strong interactions and is no longer restricted by Fermi-surface phase-space effects. To develop a well-controlled approach of this regime is an important question in the theory of strongly correlated electrons. In this talk I will give an overview over the description of incoherent and critical electronic systems using the Sachdev-Ye-Kitaev approach. We consider versions of the model where electrons interact with each other, with boson collective modes, and even with phonons. We also comment on the very direct relation to holographic approaches to strongly coupled quantum theories. Finally we address the emergence of superconductivity in such an incoherent metal and show that pairing and superconductivity of a fully incoherent electronic system is allowed and leads to a pairing state with high transition temperature but low condensation energy.

Seminarroom 1+2+3

12 Aug 2019

04:30 PM

04:30 PM

Genetically identical microbial cells often display diverse phenotypes. Stochasticity at the single-cell level contributes significantly to this phenotypic variability, and cells utilize a variety of mechanisms to regulate noise. In turn, these control mechanisms lead to correlations in various cellular traits across the lineage tree. I will present recent models we developed for understanding cellular homeostasis, with special focus on protein levels and cell size. These models allow us to characterize single-cell variability, including the emerging correlations and distributions. I will discuss the implications of stochasticity on the population growth. In contrast to the dogma, we find that variability may be detrimental to the population growth, suggesting that evolution would tend to suppress it.

Seminarroom 1+2

26 Aug 2019

04:30 PM

04:30 PM

A few tricks (hydrophobic texture, Leidenfrost state, etc.) allow us to keep water drops with a spherical shape, which induces spectacular properties. We describe a few of them. We also challenge the water mobility in the cases where it is expected to be impeded - for instance by reducing the drop size or by increasing the water temperature.

Seminarroom 1+2

16 Sep 2019

04:30 PM

04:30 PM

In quantum magnets spins form well-defined lattices and serve as model systems to study many-body quantum phases such as interacting quantum-dimer qubits, spin Luttinger-liquids, Bose glasses, or magnon Bose-Einstein condensates. Neutron, muon and photon sources are unique tools for high-precision studies of such phases, and of their correlations and excitations in as well as out of equilibrium. An overview of current frontiers in the field will be presented with special focus on recent developments in computational physics and exciting new opportunities that free electron lasers like SwissFEL and European XFEL will offer to study the time-dependence and out-of-equilibrium quantum mechanics of such systems.

Seminarroom 1+2+3

30 Sep 2019

04:30 PM

04:30 PM

In a 2D world, most transitions towards ordered states of matter like crystals or magnets would not occur because of the increased role of fluctuations. However, non-conventional topological transitions can still occur, as understood by Kosterlitz and Thouless (2016 Nobel prize). In this talk I will present some important features of Flatland physics explored with cold atomic gases, and connect them with other prominent topological properties of matter, such as quantum-Hall type phenomena.

Seminarroom 1+2

07 Oct 2019

04:30 PM

04:30 PM

We first review the basic idea of using machine learning in conjunction with a limited duration of time series data to construct a closed-loop, autonomous, dynamical system that can predict the future evolution of the state of the unknown system that generated the data [1]. Using the reservoir computing type of machine learning, we then present examples of extensions and applications of this idea. These will include a parallel implementation enabling forecasting of the states of very large spatiotemporally chaotic systems with local interactions [2], a hybrid scheme where an imperfect knowledge-based model component is combined with a limited-size machine learning component to achieve prediction performance much better than that of either of the components acting alone [3], an architecture combining the parallel and hybrid schemes, and generalization of ensemble Kalman filtering to cyclic prediction using the parallel/hybrid machine learning schemes. As an example of the potential utility of these elements for large complex spatiotemporally chaotic systems, their use in our ongoing project on improving weather forecasting [4] will be outlined. [1] Jaeger, Haas, Science (2004). [2] Pathak, Hunt, Girvan, Lu, Ott, Phys Rev Lett (2018). [3] Pathak, Wikner, Fussell, Chandra, Hunt, Girvan. Ott, CHAOS (2018). [4] Collaborators on our current weather forecasting project: T. Acomano, M. Girvan, B. Hunt, G. Katz, J. Reggia, I. Szunyogh, C.-Y. Wang, A. Wikner.

Seminarroom 1+2

21 Oct 2019

04:30 PM

04:30 PM

Fluid flows can induce long-ranged interactions and propagate information on large scales. Especially during the development of an organism, coordination on large scales is essential. What are the principal mechanisms of how fluid flows induce, transmit and respond to biological signals and thus control morphology? Fluid flows are particularly prominent during the growth and adaptation of transport networks. Here, the network-forming slime mold Physarum polycephalum emerged as a model system. Investigating the pivotal role of fluid flows in this live transport network we find that flows are patterned in a peristaltic wave across the network thereby optimizing transport. In fact, flows are hijacked by signals to propagate throughout the network. This simple mechanism is sufficient to explain surprisingly complex dynamics of the organism like scaling of peristaltic wave with network size and finding the shortest path through a maze.

Seminarroom 1+2

28 Oct 2019

04:30 PM

04:30 PM

In this talk I will discuss ongoing efforts at UChicago to explore matter made of light. I will begin with a broad introduction to the challenges associated with making matter from photons, focusing specifically on (1) how to trap photons and imbue them with mass and charge; (2) how to induce photons to collide with one another; and (3) how to drive photons to order, by cooling or otherwise. I will then provide as examples two state-of-the-art photonic quantum matter platforms: microwave photons coupled to superconducting resonators and transmon qubits, and optical photons trapped in multimode optical cavities and made to interact through Rydberg-dressing. In each case I will describe a synthetic material created in that platform: a Mott insulator of microwave photons, stabilized by coupling to an engineered, non-Markovian reservoir, and a Laughlin molecule of optical photons prepared by scattering photons through the optical cavity. Indeed, building materials photon-by-photon will provide us with a unique opportunity to learn what all of the above words mean, and why they are important for quantum-materials science. Finally, I will conclude with my view of the broad prospects of photonic matter in particular, and of synthetic matter more generally.

Seminarroom 1+2

25 Nov 2019

04:30 PM

04:30 PM

Topological insulators are a novel class of materials that exhibit a novel state of matter – while the inside (bulk) of the materials is electrically insulating, their surface is metallic. This effect occurs because the band structure of the materials is topologically different (in a mathematical sense) from the outside world. This talk describes our discovery of this type of behavior while studying the charge transport properties of thin, two-dimensional layers of the narrow-gap semiconductor HgTe. These layers exhibit the quantum spin Hall effect, a quantized conductance which occurs when the bulk of the material is insulating. Using various tricks one can show that the transport occurs along one-dimensional, spin-polarized channels at the edges of the sample. Also thicker HgTe samples can be turned into topological insulators, but now the surface states are two-dimensional metallic sheets. The metal in these sheets is rather exotic in that the band structure is similar to that encountered for elementary particles – the charge is carried by so-called Dirac fermions. This means that experiments on these layers can be used to test certain predictions from particle theory that are difficult to access otherwise. As an example, I will describe experiments where a supercurrent is induced in the surface states by contacting these structures with Nb electrodes. AC investigations indicate that the induced superconductivity is strongly influenced by the Dirac nature of the surface states. We present strong evidence for the presence of a gapless Andreev mode in our junctions. Finally, by playing with the strain in the layers, we can turn HgTe into a Dirac semimetal, which exhibits the ‘axial anomaly’ known from particle physics when the Fermi level is tuned to the Dirac points.

Seminarroom 1+2

22 Jan 2018

04:30 PM

04:30 PM

The stable generation of high temperature Hydrogen plasmas (ion and electron temperature in the range 10-20 keV) is the basis for the use of nuclear fusion to generate heat and thereby electric power. The most promising path is to use strong, toroidal, twisted magnetic fields to confine the electrically charged plasma particles in order to avoid heat losses to the cold, solid wall elements. Two magnetic confinement concepts have been proven to be most suitable: (a) the tokamak and (b) the stellarator. The stellarator creates the magnetic field by external coils only, the tokamak by combining the externally created field with the magnetic field generated by a strong current in the plasma. “Wendelstein 7-X” is the name of a large superconducting stellarator that goes into operation after 15 years of construction. With 30 $m^3$ plasma volume, 3 T magnetic field on axis, and 10 MW micro wave heating power, Hydrogen plasmas are generated that allow one to establish a scientific basis for the extrapolation to a future fusion power plant. It is a unique feature of Wendelstein 7-X to be able to operate high-power Hydrogen plasmas under steady-state conditions, more specifically for 1800 s (note that the world standard is now in the 10 s ballpark). This talk provides a review of the principles of nuclear fusion and discusses the key physics subjects of optimized stellarators. The sometimes adventurous undertaking to construct such a first-of-a-kind device is summarized as well as the most important findings during the first operation phase of Wendelstein 7-X. We finish with an outlook towards the fusion power station and address the most important remaining issues to be addressed in the framework of the world-wide fusion research endeavor.

Seminarroom 1+2+3

07 Feb 2018

04:30 PM

04:30 PM

The hard-disk model has exerted outstanding influence on computational physics and statistical mechanics. Decades ago, hard disks were the first system to be studied by reversible Markov-chain Monte Carlo methods satisfying the detailed-balance condition and by molecular dynamics. It was in hard disks, through numerical simulations, that a two-dimensional melting transition was first seen to occur even though homogeneous short-range interacting particle systems cannot develop crystalline order. Analysis of the system was made difficult by the absence of powerful simulation methods. In recent years, we have developed a class of irreversible event-chain Monte Carlo algorithms that violate detailed balance. They realize thermodynamic equilibrium as a steady state with non-vanishing probability flows. A new factorized Metropolis filter turns them into a paradigm for general Monte Carlo calculations. I will in particular show how the event-chain Monte Carlo algorithm has allowed us to demonstrate that hard disks melt with a first-order transition from the liquid to the hexatic and a continuous transition from the hexatic to the solid. Event-chain computations have also lead to our new understanding of two-dimensional melting for soft disks, that has been intensely studied in experiment. Finally, I will discuss two-dimensional melting on a substrate (as it is realized in skyrmion systems), and for active particles, and will present a very recent application of the event-chain algorithm to Coulomb-type long-range-interacting systems.

Seminarroom 1+2+3

26 Feb 2018

04:30 PM

04:30 PM

Ultra cold atoms are remarkable systems with a truly unprecedented level of experimental control and one application of this control is creating topological band structures. The most natural approach centers on creating suitable real-space lattice potentials that the atoms experience. Here we present our experimental work which uses the internal atomic states as an additional ``synthetic'' dimension. We engineered a two-dimensional magnetic lattice in an elongated strip geometry, with effective per-plaquette flux about 4/3 times the flux quanta. The long direction of this strip is formed from a 1D optical lattice while the short direction is built from the 5 mF states comprising the f=2 ground state hyperfine manifold of Rb-87. We imaged the localized edge and bulk states of atomic Bose-Einstein condensates in this strip, with single lattice-site resolution along the narrow direction. In this 5-site wide strip we are able to delineate between bulk behavior quantified by Chern numbers and edge behavior which is not.

Seminarroom 1+2+3

05 Mar 2018

04:30 PM

04:30 PM

Since the mid-nineties of the 20th century, it became apparent that one of the centuries’ most important technological inventions, computers in general and many of their applications could possibly be further enhanced by using operations based on quantum physics. This is timely since the classical roadmap for the development of computational devices, commonly known as Moore’s law, will cease to be applicable within the next decade. This is due to the ever-smaller sizes of the electronic components that will enter the realm of quantum physics. Computations, whether they happen in our heads or with any computational device, always rely on real physical devices and processes. Data input, data representation in a memory, data manipulation using algorithms and finally, data output require physical realizations with devices and practical procedures. Building a quantum computer then requires the implementation of quantum bits (qubits) as storage sites for quantum information, quantum registers and quantum gates for data handling and processing as well as the development of quantum algorithms. In this talk, the basic functional principle of a quantum computer will be reviewed. It will be shown how strings of trapped ions can be used to build a quantum information processor and how basic computations can be performed using quantum techniques. In particular, the quantum way of doing computations will be illustrated with analog and digital quantum simulations, which range from the simulation of quantum many-body spin systems over open quantum systems to the quantum simulation of a lattice gauge theory.

Seminarroom 1+2+3

19 Mar 2018

04:30 PM

04:30 PM

The statistical mechanics of equilibrium systems is characterized by two fundamental ideas: that closed systems approach a late time thermal state and that of phase structure wherein such late time states exhibit singular changes as various parameters characterizing the system are changed. Recent progress has established generalizations of these ideas which apply to periodically driven, or Floquet, closed quantum systems. I will describe this progress, which centrally uses other recent advances in our understanding of many body localization. I will describe how it has resulted in the discovery of entirely new phases such as the Pi-spin glass/Floquet time crystal which exist only in driven quantum systems.

Seminarroom 1+2

26 Mar 2018

04:30 PM

04:30 PM

Bose-Einstein condensation has been observed with cold atomic gases, exciton-polaritons, and more recently with photons in a dye-solution filled optical microcavity. I will here describe measurements of my Bonn group observing the transition between usual lasing dynamics and photon Bose-Einstein condensation. The photon Bose-Einstein condensate is generated in a wavelength-sized optical cavity, where the small mirror spacing imprints a low-frequency cutoff and photons confined in the resonator thermalize to room temperature by absorption re-emission processes on the dye molecules. This allows for a particle-number conserving thermalization, with photons showing a thermodynamic phase transition to a macroscopically occupied ground state, the Bose-Einstein condensate. When the thermalization by absorption and re-emission is faster than the photon loss rate in the cavity, the photons accumulate at lower energy states above the cavity cutoff, and the system finally thermalizes to a Bose-Einstein condensate of photons. On the other hand, for a small reabsorption with respect to the photon loss, the state remains laser-like. I will also report recent measurements of the heat capacity of the photon gas, which were performed under the conditions of the thermalization being much faster than both photon loss and pumping. At the Bose-Einstein phase transition, the observed specific heat shows a cusp-like singularity, as in the $\lambda$-transition of liquid helium, illustrating critical behavior of the photon gas. In my talk, I will begin with a general introduction and give an account of current work and future plans of the Bonn photon gas experiment.

Seminarroom 1+2+3

09 Apr 2018

04:30 PM

04:30 PM

A variety of one-dimensional electronic systems can be engineered to host topological superconductivity and Majorana zero modes. In this talk, I’ll describe experiments on two different one-dimensional platforms. One is based on chains of magnetic atoms the work on which grew out of early efforts on the study of localized Bogoliubov quasi-particles near individual magnetic atoms on a superconductors. We have now performed a series of experiments to establish the presence of Majorana’s in this system, including a recent study of their spin polarization. A second system is based on introducing superconductivity on the hinge states of a high order topological insulator. Using combination of magnetism and superconductivity, we are exploring how Majorana zero mode can emerge in this system.

Seminarroom 1+2+3

16 Apr 2018

04:30 PM

04:30 PM

Actin filaments are the essential components of the cytoskeleton that provide the elasticity of a cell. In a cell they interact with many proteins and in particular molecular motors. This talk will present 3 biological situations where actin filaments interact with molecular motors in relation with important cellular functions : the control of actin polymerization, intracellular transport and cell migration. Actin filaments are treadmilling : they grow at one end and depolymerize at the other end. The first example of interaction between actin and molecular motors deals with the induced depolymerization of actin filaments by myosin1b molecular motors studied in motility assays. The depolymerization requires a catch bond motor with a detachment rate decreasing strongly when the motor is under force Molecular motors navigate the cytoskeleton to position vesicles and organelles at specific locations in the cell. In order to understand this transport process, the group of Pascal Martin at Institut Curie has used an antiparallel network of overlapping filaments. Beads coated with myosin motors accumulate at the midline of the pattern. The accumulation is well described by a three-state model of bead transport, in which active beads locally sense the net polarity of the filament network by frequently detaching from and reattaching to the filaments. The migration of immune cells is guided by several chemical signals, but also by physical cues such as the hydraulic resistance of the vessels in which they travel. This barotaxis effect has been studied in vitro by the groups of M. Piel and A.M. Lenon using microfluidic channels. We show that barotaxis results from a force imbalance at the scale of the cell, amplified at the scale of a network of vessels.

Seminarroom 1+2+3

23 Apr 2018

04:30 PM

04:30 PM

Electro-mechanical excitation waves in the heart may exhibit different spatio-temporal dynamics ranging from repeated plane waves to scroll waves or spatio-temporal chaos, resulting in life threatening arrhythmias. This kind of chaotic dynamics in excitable cardiac media is often characterised by significant complexity fluctuations (including laminar phases) and can be non-persistent exhibiting supertransients, with lifetimes of the chaotic phases increasing exponentially with the system size. Terminating or at least shortening chaotic transients can be life saving in the medical context of cardiac arrhythmias. Therefore, we study the impact of perturbations on the duration of transients and features of the terminal phase of chaotic transients. Practically, such perturbations can be applied via so-called virtual electrodes where electrical heterogeneities of the cardiac muscle act as local excitation sites when subjected to a global electric field. In the talk we shall present novel results on the nonlinear dynamics of the heart including features of the terminal phase of transient chaos, parameter and state estimation, as well as experimental studies and modalities.

Seminarroom 1+2+3

07 May 2018

04:30 PM

04:30 PM

For the macroscopic world, classical thermodynamics formulates the laws governing the transformation of various forms of energy into each other. Stochastic thermodynamics extends these concepts to micro- and nano-systems embedded or coupled to a heat bath where fluctuations play a dominant role. Examples are colloidal particles in time-dependent laser traps, single biomolecules manipulated by optical tweezers or AFM tips, and transport through quantum dots. For these systems, exact non-equilibrium relations like the Jarzynski relation, fluctuation theorems and, most recently, a thermodynamic uncertainty relation have been discovered. First, I will introduce the main principles and show a few representative experimental applications. In the second part, I will discuss the universal trade-off between the thermodynamic cost and the precision of any biomolecular, or, more generally, of any stationary non-equilibrium process. By applying this thermodynamic uncertainty relation to molecular motors, I will introduce the emerging field of "thermodynamic inference" where relations from stochastic thermodynamics are used to infer otherwise yet inaccessible properties of (bio)physical and (bio)chemical systems.

Seminarroom 1+2+3

14 May 2018

04:30 PM

04:30 PM

We introduce the broad field of active matter, a novel class of non-equilibrium materials composed of many interacting units that individually consume energy and collectively generate motion or mechanical stresses. Unlike swarms of fish and flocks of birds, cells or ants can support static loads because cells are bound by transient links. This leads to the concept of “entangled active matter” , which emerged recently to provide a unified understanding of the behavior of swarms of adhesive particles ranging from vibrating staples, to ants, and to cellular aggregates [1]. Recently we have focused on cellular aggregate – nanoparticles hybrid systems. This system is of great interest as it has been previously shown that particles can modify the mechanical properties of cells in terms of adhesion area, proliferation and motility. We study both small particles (up to few microns), which are digested by cells by endocytosis and phagocytosis, and larger particles, which do not enter in the cells, leading to a completely different physics. Nanostickers (size 20 nm ) [2] We show that nanoparticles, within a limited size range, can be used as a glue “nanostickers”to enable the formation of self-assembled aggregates by promoting cell–cell interactions. We model the cell-cell adhesion induced by the nanostickers using a three states dynamical model where the NPs are free, adsorbed on the membrane or internalized by endocytosis. We find that carboxylated polystyrene NPs are more efficient than the silica NPs of the same size, which were reported to induce fast wound healing and to glue soft tissue by Leibler et al. Nanostickers by increasing the cohesion of tissues and tumors may have important applications for cellular therapy and cancer treatment. Microparticles ( size 1micron): gluttonous cells[3]. We study the spreading of cell aggregates deposited on adhesive substrates decorated with microparticles. A cell monolayer expands around the aggregate. The cells at the periphery uptake the microparticles by phagocytosis, clearing the substrate and forming an aureole of cells full of particles. We study the dynamics of spreading, the width of the aureole, and the level of cell internalization as a function of the size, nature and density of the beads. The radius and width of the aureole allow quantification of the MP volume fraction incorporated by the cell, leading to an easy, fast, and inexpensive cell – particle internalization measurement. Macroparticles ( size 2-20 microns) ”Activated Brownian motion” Performing the same experiment with particles which are too big to be eaten, we observed that they are put into motion by the cells.We also describe also the mechanical properties of hybrid particles-cells aggregates (surface tension, elastic modulus, viscosity) using pipette aspiration technique [4], the phase separation between dead and living matter and how they spread . [1] F Brochard-Wyart et al, Entangled Active Matter: from ants to living cells EPJE 2015 [2] B.Brunel et al Nanostickers for cells: a model study using cell–nanoparticle hybrid aggregates Soft Matter 12 (38), 7902-7907. 2015 [3] Grégory Beaune^1 et al *5,6How gluttonous cell aggregates clear substrates coated with microparticles, Scientific Reports 7, Article number: 15729 (Nov 2017).[4] David Gonzalez-Rodriguez et al. Soft Matter Models of developing Tissues and Tumors. Science 338, 910; 1226418 (2012)

Seminarroom 1+2+3

11 Jun 2018

04:30 PM

04:30 PM

The atmosphere, ocean, and other components of the climate system behave in a fairly irregular way. A major surprise of the late 20th century was the realization that such behavior could be produced by natural systems with a small number of degrees of freedom, governed by fully deterministic, but nonlinear laws. Still, the climate system has a large number of degrees of freedom, and ample room for random factors to intervene. Can we reconcile a low-order, deterministically nonlinear description of weather or climate with a high-order, possibly linear but random one? This talk will present some steps on the road to such a "grand unification," and implications for climate variability, sensitivity and predictability will be discussed. References: 1. Ghil, M., 2002: Natural climate variability, in Encyclopedia of Global Environmental Change, T. Munn (Ed.), Vol. 1, J. Wiley & Sons, Chichester/New York, pp. 544–549. 2. Ghil, M., 2014: Climate variability: Nonlinear and random aspects, in Encyclopedia of Atmospheric Sciences, 2nd edn., G. R. North, J. Pyle and F. Zhang (Eds.), Elsevier, vol. 2, pp. 38–46. 3. Ghil, M., 2017: The wind-driven ocean circulation: Applying dynamical systems theory to a climate problem, Discr. Cont. Dyn. Syst. – A, 37(1), 189–228, doi:10.3934/dcds.2017008.

Seminarroom 1+2+3

18 Jun 2018

04:30 PM

04:30 PM

Tensor networks are an efficient representation of interesting many-body wavefunctions and underpin powerful algorithms for strongly correlated systems. But tensor networks could be applied much more broadly than just for representing wavefunctions. Large tensors similar to wavefunctions appear naturally in certain families of models studied extensively in machine learning. Decomposing the model parameters as a tensor network leads to interesting algorithms for training models on real-world data which scale better than existing approaches. In addition to training models directly for recognizing labeled data, tensor network real-space renormalization approaches can be used to extract statistically significant "features" for subsequent learning tasks. I will also highlight other benefits of the tensor network approach such as the flexibility to blend different approaches and to interpret trained models.

Seminarroom 1+2+3

25 Jun 2018

04:30 PM

04:30 PM

Seminarroom 1+2+3

02 Jul 2018

04:30 PM

04:30 PM

Abstract: Quasicrystals are exotic materials with symmetries that were once thought to be impossible for matter. The first known examples were synthesized in the laboratory over 35 years ago, but could Nature have beaten us to the punch? This talk will describe the search that took over a dozen years to answer this question, resulting in one of the strangest scientific stories you are ever likely to hear.

Seminarroom 1+2

23 Jul 2018

04:30 PM

04:30 PM

At the turn of the 20th century, physicists faced an uncanny range of unsolved problems: simple questions, such as why hot objects change color, why matter is hard and why the sun keeps on shining, went unanswered. These problems heralded a new era of quantum physics. What was truly remarkable about discovery in this heroic era, was the intertwined nature of research in the lab and in the cosmos: solving superconductivity really did help answer why the sun keeps on shining, while looking at the stars provided clues as to why matter is hard. The challenges facing us today, epitomized by our failure to quantize gravity and the mysteries of dark matter and energy, are not just problems facing particle physics and astronomy, but problems that challenge physics to its core. What is perhaps less well known, is that physics in the lab and cosmos are just as intertwined today, as they were a hundred years ago. I will talk today about the less well-known dark matter challenges of the solid state, epitomized by the strange metals with linear resistivity that accompany high temperature superconductivity, the recent discovery of insulators with Fermi surfaces and quantum criticality - the solid-state version of a black hole in the phase diagram. The solution of these laboratory-scale problems fundamentally challenge our understanding of emergent quantum matter, and they are no less intertwined with their cosmological counterparts than they were a hundred years ago. I will highlight three Dark-Matter challenges that have arisen in heavy fermion physics[1-4], emphasizing their connections with other strongly correlated quantum materials and discussing some of our recent theoretical efforts to make progress on them: quantum criticality, hidden order and the possibility of new classes of broken symmetry outside the Hartree-Fock/BCS paradigm and topology [5]. [1] Piers Coleman, “Heavy Fermions and the Kondo Lattice, a 21st Century Perspective”, arXiv:1509.05769 (2015). [2] Joe Thompson and Zachary Fisk, “Progress in Heavy Fermion Superconductivity: Ce115 and other materials”, J. Phys. Soc. Jpn. 81, 011002 (2012). [3] Philipp Gegenwart, Qimiao Si and Frank Steglich, ”Quantum criticality in heavy-fermion metals”,Nature Physics 4, 186 - 197 (2008). [4] Maxim Dzero et al, “Topological Kondo Insulators”, arXiv 1506.05635, Ann. Rev. Cond. Matt. Phys., Volume 7:249-280 (2016). [5] B. S. Tan et. al, “Unconventional Fermi surface in an insulating state”, Science 349, 287-290 (2015).

Seminarroom 1+2

13 Aug 2018

04:30 PM

04:30 PM

The prospect of judiciously utilizing both optical gain and loss has been recently suggested as a means to control the flow of light. This proposition makes use of some newly developed concepts based on non-Hermiticity and parity-time (PT) symmetry-ideas first conceived within quantum field theories. By harnessing such notions, recent works indicate that novel synthetic structures and devices with counter-intuitive properties can be realized, potentially enabling new possibilities in the field of optics and integrated photonics. Non-Hermitian degeneracies, also known as exceptional points (EPs), have also emerged as a new paradigm for engineering the response of optical systems. In this talk, we provide an overview of recent developments in this newly emerging field. The use of other type symmetries in photonics will be also discussed.

Seminarroom 1+2

27 Aug 2018

04:30 PM

04:30 PM

Thirty years ago, scientists first observed that when a small amount of gold is deposited on the surface of silicon, both the gold and silicon atoms automatically organize themselves into parallel linear rows, so-called "atom chains", with nearly perfect structural order. This observation marked the beginning of a new research direction in which theoretical predictions about "physics in one dimension" could now be investigated experimentally using the standard tools of surface science such as scanning tunneling microscopy, x-ray diffraction, and photoemission. A particularly striking discovery, first reported ten years ago, was that at low temperature the silicon chains can develop local magnetic moments, which form regular highly ordered, periodic patterns. These "silicon spin chains" have now become the main focus of this research field. This talk will describe three recent theoretical and experimental aspects of silicon spin chains: the possibility of magnetic ordering in these one-dimensional systems; the prospects for using surface chemistry to tailor spin chains by creating or destroying individual spins; and the properties and dynamics of solitons in the spin chains.

Seminarroom 1+2+3

10 Sep 2018

04:30 PM

04:30 PM

Thermodynamics of superconducting quantum circuits Superconducting circuits provide a platform for stochastic thermodynamics experiments in both classical and quantum regimes (“circuit Quantum Thermodynamics”). I first review the ideas, principles and examples of classical experiments utilizing single electron charge as the stochastic variable. I present experiments over the past several years on classical fluctuation relations and Maxwell Demons (MD), the latter in form of both non-autonomous Szilard Engines and autonomous MDs. Recent highlights on entropy reduction and rare events will be reviewed. In the second part of the talk I focus on open quantum systems formed of superconducting qubits and resonators, coupled to heat baths. In this context microwave photons carry the heat between the system and bath. I present experiments on quantum heat transport mediated by a transmon qubit, progress on superconducting quantum heat engines and refrigerators, and on detecting single microwave photon quanta. Success in the last item would allow us to perform true stochastic thermodynamics experiments in the quantum regime, and to realize quantum MDs.

Seminarroom 1+2

24 Sep 2018

04:30 PM

04:30 PM

A fundamental assumption in statistical physics is that generic closed quantum many-body systems thermalise under their own dynamics. Recently, the emergence of many-body localised (MBL) systems has questioned this concept, challenging our understanding of the connection between statistical physics and quantum mechanics. In my talk, I will report on several recent experiments carried out in our group on the observation of Many-Body Localisation in different scenarios, ranging from 1D fermionic quantum gas mixtures in driven and undriven Aubry-André type disorder potentials and 2D systems of interacting bosons in 2D random potentials. It is shown that the memory of the system on its initial non-equilibrium state can serve as a useful indicator for a non-ergodic, MBL phase. Furthermore, I will present new results on the slow relaxation dynamics in the ergodic phase below the MBL transition and experiments that explore the resilience of a 2D MBL phase when coupled to a finite thermal bath. Our experiments represent a demonstration and in-depth characterisation of many-body localisation, often in regimes not accessible with state-of-the-art simulations on classical computers.

Seminarroom 1+2+3

15 Oct 2018

04:30 PM

04:30 PM

In Reinforcement Learning an agent learns how to act in an environment in order to achieve desired goals. In general, the agent only has access to partial information from the world, and has to learn how to act appropriately in face of this uncertainty. One of the earliest results in the theory of Optimal Control (Feldbaum 1965) demonstrates that in order to act appropriately, the agent must also probe the environment in order to gain information and reduce uncertainty. In other words, exploring the environment is an essential component of learning to act. However, very few provably effective procedures were proposed in the control literature to solve this problem. In recent years, several elegant solutions to the problem of exploration have been proposed in the Machine Learning literature for the case of finite state and action spaces (which was of little concern to the control theorists). However, the problem of effective exploration in continuous spaces is still very much open, and of increasing importance in many applications. We survey some recent approaches to exploration in continuous domains, in both model based and model free settings, and suggest open problems for future research.

Seminarroom 1+2

22 Oct 2018

04:30 PM

04:30 PM

The interplay between fluid flows and living organisms plays a major role in the competition and organization of microbial populations in liquid environments. Hydrodynamic transport leads to the dispersion, segregation or clustering of biological organisms in a wide variety of settings. To explore such questions, we have created microbial range expansions in a laboratory setting by inoculating two identical strains of S. cerevisiae (Baker’s yeast) with different fluorescent labels on a nutrient-rich fluid 10^4 to 10^5 times more viscous than water. The yeast metabolism generates intense flow in the underlying fluid substrate several times larger than the unperturbed colony expansion speed. These flows dramatically impact colony morphology and genetic demixing, triggering in some circumstances a fingering instability that allows these organism to spread across an entire Petri dish in roughly 24 hours. We argue that yeast colonies create fluid flow by consuming nutrients from the surrounding fluid, decreasing the fluid’s density, and ultimately triggering a baroclinic instability when the fluid’s pressure and density contours are no longer parallel. Our results suggest that microbial range expansions on viscous fluids will provide rich opportunities to study the interplay between advection and spatial population genetics.

Seminarroom 1+2

29 Oct 2018

04:30 PM

04:30 PM

Active matter comprises particles whose microscopic dynamics breaks time-reversal symmetry (TRS) via the continuous conversion of fuel into motion, resulting in entropy production at the microscopic scale. Examples include bacteria and synthetic self-propelled colloids. Equilibrium statistical physics concepts, for instance the Boltzmann distribution, are not applicable to active matter because these concepts assume the TRS of the underlying microscopic laws. When viewed at a coarse grained level, the microscopic absence of TRS may either remain obvious at large scales or become almost undetectable. In the latter case, we retain the hope that equilibrium concepts, at least in some modified form, may be applicable. This talk will discuss the conceptual toolbox needed to characterize the presence or absence of TRS at coarse-grained level, focusing on global and local measures of entropy production. Put differently: when, and how, can you tell whether life's movie is running backwards?

Seminarroom 1+2

05 Nov 2018

04:30 PM

04:30 PM

In high oxidation state oxides like the trivalent Nickel oxides, tetravalent Co and Fe oxides as well as the parent superconductors BaBiO3 and SrBiO3 and High Tc hole doped cuprates, the cation electron affinity in the formal valence could end up larger than the O 2- ionization potential leading to a so called negative charge transfer gap. If the charge transfer energy is strongly negative, then we should really adopt starting electronic configurations such as Ni2+ rather than 3 + or Bi 3+ rather than 4+ with compensation holes in the O 2p valence band for charge neutrality. If in addition the lowest energy cation ionization states are strongly hybridized with the valence O 2p states the low energy scale electronic structure and be well described by a molecular orbital type of approach (1,2). This is a new approach to the Wannier function description (3) but with explicit inclusion of the O states which provides a natural path to inclusion of the electron phonon coupling, charge density wave formation, potential bipolaron formation and paring interactions in superconductors. We discuss recent developments in this approach and show that the effective electron phonon coupling involving these molecular like orbitals is much stronger than that estimated from density function approaches. We also show that this leads to Peierls like charge density wave like ground states and we describe how the electron phonon coupling involving the hopping integrals rather than the on-site energies evolves into a large effective attractive interaction between low energy scale electrons. I will also briefly describe how these effects lead to our coelution that the ion battery material LiNiO2 should be viewed as an “entropy-stabilized charge- and bond-disproportionated glass”.

Seminarroom 1+2+3

12 Nov 2018

04:30 PM

04:30 PM

The quantum optical control of solid-state mechanical devices, quantum optomechanics, has emerged as a new frontier of light-matter interactions. Devices currently under investigation cover a mass range of more than 17 orders of magnitude - from nanomechanical waveguides of some picograms to macroscopic, kilogram-weight mirrors of gravitational wave detectors. This development has been enabled by the insight that quantum optics provides a powerful toolbox to generate, manipulate and detect quantum states of mechanical motion, in particular by coupling the mechanics to an optical or microwave cavity field. Originally, such cavity optomechanical systems have been studied from the early 1970s on in the context of gravitational wave antennas. Advancements in micro-fabrication and micro-cavities, however, have resulted in the development of a completely new generation of nano- and micro-optomechanical devices. Today, 10 years after the first demonstrations of laser cooling of micromechanical resonators, the quantum regime of nano- and micromechanical motion is firmly established. Recent experimental achievements include the generation of genuinely non-classical states of micromechanical motion such as quantum squeezing and entanglement. This level of control over solid-state mechanical degrees of freedom is now also being utilized in diverse application domains ranging from classical sensing, to low-noise optical coatings for precision interferometry, and also to photon-phonon quantum interfaces. From the fundamental physics point of view, one of the fascinating prospects of quantum optomechanics is to coherently control the motional degree of freedom of a massive object in an unprecedented parameter regime of large mass and long coherence time, hence opening up a new avenue for macroscopic quantum experiments. The availability of quantum superposition states involving increasingly massive objects could enable a completely new class of experiments, in which the source mass character of the quantum system starts to play a role. This addresses directly one of the outstanding questions at the interface between quantum physics and gravity, namely “how does a quantum system gravitate?”.

Seminarroom 1+2

03 Dec 2018

04:30 PM

04:30 PM

Ensembles of atoms or other quantum emitters are envisioned to be an important component of quantum applications, ranging from quantum memories for light to photon-photon gates to metrology. It has historically been an outstanding challenge to exactly solve for the quantum dynamics of an optical field as it propagates through and interacts with an ensemble. The standard axiomatic approach is to use the one-dimensional Maxwell-Bloch equations, which treats the interaction between the ensemble and a quasi-1D optical mode of interest, while the interaction with the remaining 3D continuum of modes is assumed to result in independent spontaneous emission of excited atoms. Strictly speaking, this assumption cannot be correct, as the emission of light is a wave phenomenon, and thus the emitted intensity must depend on interference and correlations between the atoms. Here, we discuss an alternative theoretical approach, which accounts for interference and the precise atomic positions. In this formalism, an interacting quantum spin model describes the dynamics of the atomic internal degrees of freedom under multiple photon scattering, while the field properties can subsequently be re-constructed from the spin correlations. Using this model, we then show how interference can be exploited as an extremely powerful resource to suppress the unwanted emission of light and the subsequent loss of information into undesirable directions. The effects of interference are particularly prominent in ordered arrays of emitters. As two specific examples, we construct a new protocol for a quantum memory for light based upon an ordered array, whose error rate as a function of system resources scales exponentially better than previously known bounds. We also show the interrogation time in an optical lattice clock can be significantly extended, through the excitation of collective subradiant atomic states whose spontaneous emission rates are strongly suppressed. These results raise the intriguing question of whether interference can be used to broadly re-define the performance limits of all applications involving atomic light-matter interfaces.

Seminarroom 1+2

06 Feb 2017

04:30 PM

04:30 PM

Seminarroom 1+2+3

13 Feb 2017

04:30 PM

04:30 PM

Ultrafast and nano-optics: Watching the motion of electrons in nanostructures

Seminarroom 1+2+3

27 Feb 2017

04:30 PM

04:30 PM

Seminarroom 1+2+3

27 Mar 2017

04:30 PM

04:30 PM

In recent years many physicists researching quantum materials have become very excited about an unusual state of matter: the quantum spin liquid (QSL). In this talk I will explore the difference between “conventional” ordered magnetic systems and QSLs. To understand these systems the way physicists do one needs to appreciate the importance of collective elementary excitations. In ordinary magnets these are called spin-waves, or, in the quantum version, magnons. These will be explained and discussed along with other excitations that are important in quantum magnetism sometime called “triplons” and spinons. I will discuss a major technique for characterizing these excitations: inelastic neutron scattering. The last part of the talk will examine one material of particular recent interest: $\alpha-RuCl_3$. This material orders magnetically, but it is close to a special kind of quantum spin liquid called the “Kitaev quantum spin liquid”, and exhibits unusual excitations that might be related to particles known as Majorana Fermions. Finally, I will discuss how the magnetic order can be suppressed by either site-dilution of the magnetic $Ru^{3+}$ ions, or the application of a magnetic field. The resultant consequences on the magnetic excitation spectrum are seen to be of particular interest.

Seminarroom 1+2+3

03 Apr 2017

04:30 PM

04:30 PM

Abstract: Active materials are composed of interacting particles individually powered by motors. In this talk, we focus on chiral active materials that violate parity and time reversal symmetry. First, we show how to generate topological sound in fluids of self-propelled particles exhibiting a spontaneous chiral active flow under confinement. These topological sound modes propagate unidirectionally, without backscattering, along either sample edges or domain walls and despite overdamped particle dynamics. Next, we discuss an exotic transport coefficient characteristic of quantum Hall fluids, called odd viscosity, which controls the hydrodynamics of classical fluids composed of active rotors. This odd viscosity couples pressure to vorticity leading to transverse flow in piston compression experiments. We envision that such transverse response may be exploited to design self-assembled hydraulic cranks that convert between linear and rotational motion in microscopic machines powered by active rotors fluids.

Seminarroom 1+2+3

08 May 2017

04:30 PM

04:30 PM

Seminarroom 1+2+3

22 May 2017

04:30 PM

04:30 PM

Simple systems with only 3 or 4 interacting particles can behave in a bizarre, counter-intuitive manner. Examples to be discussed in this Colloquium include ultra-long-range Rydberg molecules with enormous electric dipole moments, as well as states of a few neutral particles that resonantly form a cluster. Moreover, insights from a few-body viewpoint can help to understand some of the rich many-body systems being actively explored, from the unitary Bose gas to the fermionic or bosonic flavors of the fractional quantum Hall effect.

Seminarroom 1+2

29 May 2017

04:30 PM

04:30 PM

RNA nanotechnology has the great potential to allow us to produce well-defined nanostructures and devices inside cells and thus open up a wide range of design opportunities in synthetic biology. To achieve this goal we need to understand the design principles of geometry, folding kinetics and topology that will allow us to genetically encode well-defined RNA nanostructures that self-assemble during the transcription process. We have recently introduced the single-stranded RNA origami method and validated the architecture by transcribing RNA tiles that assemble into lattices of different geometries. I will introduce new software tools that allow interactive design of RNA origami structures using a library of functional modules and new sequence design approaches that allow large structures to be designed. Also I will show our latest progress in developing larger three-dimensional RNA origami structures and functional RNA nanodevices with applications in biosensing and diagnostics.

Seminarroom 1+2+3

19 Jun 2017

04:30 PM

04:30 PM

Seminarroom 1+2+3

17 Jul 2017

04:30 PM

04:30 PM

Symmetries and topology play central roles in our understanding of physics. Topology explains the precise quantization of the Hall effect and the protection of surface states in topological insulators against scattering from disorder or bumps. However discrete symmetries and topology have so far played little role in thinking about the fluid dynamics of oceans and atmospheres. I show that, as a consequence of the rotation of the Earth that breaks time reversal symmetry, equatorially trapped Kelvin and Yanai waves emerge as topologically protected edge modes. Thus the oceans and atmosphere of Earth naturally share basic physics with topological insulators. As equatorially trapped Kelvin waves in the Pacific ocean are an important component of El Nino Southern Oscillation, these new results demonstrate that topology plays a surprising role in Earth’s climate system.

Seminarroom 1+2+3

24 Jul 2017

04:30 PM

04:30 PM

The central assumption of statistical mechanics is that interactions between particles establish local equilibrium. Isolated quantum systems, however, need not equilibrate; this happens, for example, when sufficient quenched disorder causes localization. The many-body localized (MBL) phase transports neither heat nor charge; may possess orders disallowed in equilibrium; and, may exhibit quantum coherence even when highly excited. In this talk, I will review the emerging understanding of how quantum localization can lead to new quantum phenomena even in highly excited states. I will give some theoretical intuition about how this might be used to build a better quantum computer and also review some of the latest experiments investigating localization.

Seminarroom 1+2+3

25 Sep 2017

04:30 PM

04:30 PM

Seminarroom 1+2+3

16 Oct 2017

04:30 PM

04:30 PM

There are many ways to study life, and one that is particularly appealing to physicists is regarding it as self-organized active soft matter that is away from equilibrium ``just the right way’’. In this Colloquium, I will discuss this notion, and provide a number of examples of how we can begin to put together simple systems - from basic ingredients that we fully understand - that would exhibit the kind of active behaviour we find in living systems. I will address the question of stability of a living system made of active components and propose a fundamentally new mechanism in which a competition between chemical signalling and cell division can determine the homeostatic conditions at the systemic level.

Seminarroom 1+2+3

date | speaker | title | |
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29 February 2016 | Satoru Nakatsuji Uni Tokyo | "Novel quantum and functional phases in correlated electron systems: from spin liquids to anomalous Hall effect in chiral antiferromagnets" | |

14 March 2016 | Eckart Meiburg | "Vorticity-based Models for Stratified Flows" | |

11 April 2016 | Peter Lu Harvard | "Modern math in medieval islamic architecture" | |

25 April 2016 | Michael Ramsey Uni Graz | "Photoemission Tomography: Why didn't we do this 30 years ago?" | |

09 May 2016 | Philipp Maass Uni Osnabrueck | "Phase Transitions in Driven Lattice Gases and Brownian Motors" | |

23 May 2016 | Sublr Sachdev Harvard | "Quantum entanglement and the phases of matter" | |

20 June 2016 | Wilhelm Zwerger | Festkolloquium P. Fulde - Dresdner Physik Kolloq. "High-temperature superconductivity below one microkelvin" | |

04 July 2016 | Roland Wiesendanger Uni Hamburg | "Nanoscale skyrmions - A new twist for spintronics" | |

03 August 2016 | Eric J. Heller | Gutzwillerkolloquium "Shedding light on condensed matter" | |

15 August 2016 | Eckhard Schöll TU Berlin | "Chimera states in complex networks" | |

29 August 2016 | Eberhard Bodenschatz MPI for Dynamics and Self-Organization | "Ciliated surfaces and transport networks" | |

12 September 2016 | David Landau University of Georgia | "Replica exchange Wnag-Landau sampling: a new paradigm for petascale Monte Carlo simulation" | |

10 October 2016 | James A. Yorke University of Maryland | "The Many Facets of Chaos" | |

17 October 2016 | Andrew Oates University College London | "Period and Patter in the Embryo" | |

28 November 2016 | Louis DiMauro Columbus, Ohio | "Strong-field probing of atomic and molecular dynamics" |

date | speaker | title | |
---|---|---|---|

26 January 2015 | Henk Stoof University Utrecht | "The sound of light" | |

20 April 2015 | Jürgen Meyer-ter-Vehn MPI für Quantenoptik, Garching | ||

18 May 2015 | Jané Kondev Brandeis University, Waltham, USA | "Chromosome Folding in Cells" | |

11 May 2015 | Ragnar Fleischmann MPI for Dynamics and Self-Organization Göttingen | "Waves in Random Media: Branched Flows and the Statistics of Extreme Waves" | |

08 June 2015 | Peter Young | Martin Gutzwiller Fellowship, Award Ceremony "Mind the gap: solving optimization problems on a quantum computer" | |

15 June 2015 | Tomas Vicsek Eötvös University, Budapest | "Quantitative approaches to hierarchy" | |

22 June 2015 | Carlo Beenakker Universität Leiden | "Chaotic scattering of Majorana fermions: complexity without complex numbers" | |

29 June 2015 | Michel Devoret Yale University | "Implementing cat-codes in Josephson quantum circuits" | |

06 July 2015 | Alex Arenas, Universitat Rovira i Virgili, Tarragona & MasonA.Porter, University of Oxford | "Introduction to Multilayer Networks" | |

13 July 2015 | Dirk van der Marel University of Geneva | "Optical detection of magnetic and electric phase-transitions in Rare-Earth Nickelates" | |

27 July 2015 | Michael Rosenblum Potsdam University | "The Kuramoto model and its extensions: synchronization transition, partial synchrony, and chimeras" | |

24 August 2015 | Alexander Govorov Ohio University | "Physics of bio-assembled nanostructures: chirality, Fano effect and hot plasmonic electrons" | |

31 August 2015 | Randy Hulet | "Many-body Physics with Ultracold Atomic Gases" | |

14 September 2015 | Charles Marcus Niels Bohr Institute, University of Copenhagen | "The status of experiments to detect and control Majorana modes in Condensed Matter systems, towards the long-term goal of topological quantum computing" | |

28 September 2015 | Hidenori Takagi MPI für Festkörperforschung Stuttgart | "Exotic electronic states produced by strong spin-orbit coupling in complex Ir oxide" | |

12 October 2015 | Joachim Krug Universität Köln | "How predictable is evolution?" |

date | speaker | title | |
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03 February 2014 | Sergei Turitsyn School of Engineering and Applied Science, Aston University | "Optical wave turbulence in fibre lasers" | |

24 March 2014 | JochenMannhart Max Planck Institute for Solid State Research, Stuttgart | "Oxide Interfaces - A Fantastic World for Electrons; From MOSFETs to Novel Electron Systems" | |

17 March 2014 | Sergey M. Bezrukov NICHD, National Institutes of Health, Bethesda, MD | "Entropy potentials in description of biological channels and other confining structures" | |

06 May 2014 | Hiroshi Sugiyama Kyoto University | "Single-Molecule Observation in the DNA Origami Nanostructures" | |

19 May 2014 | Luciano Pietronero Universita' di Roma Sapienza | "New Metrics for Economic Complexity: Measuring the Intangible Growth Potential of Countries" | |

26 May 2014 | David L. Andrews University of East Anglia, Norwich | "Photon Wave Fronts: Frontiers in Photonics" | |

16 June 2014 | Klaus Lehnertz Universität Bonn | "Large-scale epileptic networks" | |

21 July 2014 | Steve Simon University of Oxford | "Topological Matter and Why You Should Be Interested" | |

01 September 2014 | Federico Becca SISSA - International School for Advanced Studies | "Gapless and gapped spin liquids in Heisenberg models" | |

22 September 2014 | Rodolfo Jalabert IPCMS, Université de Strasbourg | "Loschmidt echo in complex systems" | |

06 October 2014 | James S. Schilling Washington University | "Contrasting Effects of Extreme Pressure on Highly Correlated Electron Behavior" | |

17 November 2014 | Jean-Luc Lehners Max-Planck-Institute for Gravitational Physics, Albert-Einstein-Institute, Potsdam-Golm | "Before the Big Bang" | |

24 November 2014 | Frank Stienkemeier Universität Freiburg | "Real-time excitation and ionization dynamics in clusters" |

date | speaker | title | |
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28 January 2013 | Claudio Castelnovo University of Cambridge | "Dynamics of fractionalised particles in condensed matter physics" | |

21 January 2013 | Gene MyersMPI of Molecular Cell Biology and Genetics, Dresden | "Building Cellular Models with Light Microscopy" | |

04 February 2013 | Ivo F. Sbalzarini Center of Systems Biology, MPI of Molecular Cell Biology and Genetics, Dresden | "Particle Methods for Computational Systems Biology" | |

11 February 2013 | Peter Grassberger University of Calgary, Canada | "The many faces of percolation" | |

18 February 2013 | Howard Stone Princeton University | "Wetting and drying of fibers " | |

15 April 2013 | Erez Hasman Technion - Israel Inst. of Technology | "Spinoptical metamaterials: spin-controlled photonics" | |

22 April 2013 | Ralf Metzler Universität Potsdam | "Ergodicity Violation and Ageing in anomalous Diffusion" | |

13 May 2013 | Thomas Elsaesser Max-Born-Institut, Berlin | "Ultrafast structural dynamics in ionic crystals mapped by femtosecond x-ray powder diffraction" | |

27 May 2013 | Tsuneyoshi Nakayama | Martin Gutzwiller Fellowship, Award Ceremony "Complex Disordered Systems: from Quantum Glass till Thermoelectric Clathrates" | |

17 June 2013 | Jacques Laskar IMCCE, Observatoire de Paris | "Frequency Map Analysis. Application to stability analysis of the solar system and particle accelerators." | |

08 July 2013 | Matthias Weidemüller Universität Heidelberg | "Dressing Photons with Rydberg Atoms" | |

01 July 2013 | Ed Grant University of British Columbia | "Penning Lattice: Dissociation and the development of spatial correlation in a molecular ultracold plasma" | |

22 July 2013 | Achim Rosch Universität Köln | "Skyrmions and monopoles in chiral magnets" | |

19 August 2013 | Heinz-Peter Breuer Universität Freiburg | ||

09 September 2013 | Mathias Fink ESPCI ParisTech, Langevin Institute | "Controlling waves at subwavelength scales in space and time through complex media" | |

16 September 2013 | Moty Heiblum Weizmann Institute of Science | "Controlled dephasing in mesoscopic systems" | |

23 September 2013 | Naoto Nagaosa RIKEN, Wako, Japan | "Topological particle in magnets – Skyrmion –" | |

30 September 2013 | Hermann Haken Universität Stuttgart | "Reminiscences on the early days of synergetics" | |

07 October 2013 | Andreas Burkert Ludwig Maximilians University, Munich | "Watching the Little Gas Cloud G2 on its Way into the Galactic Supermassive Black Hole" | |

14 October 2013 | Stefano Ruffo Università di Firenze | "Models with interactions that weakly decay with distance" | |

11 November 2013 | Vahid Sandoghdar Max Planck Institute for the Science of Light, Erlangen | "On efficient interaction of photons and atoms: from quantum optics to biophotonics" | |

18 November 2013 | Roland Wiesendanger Universität Hamburg | "Complex Spin States in Nanostructures" | |

25 November 2013 | Albert Stolow National Research Council, Canada | "Dynamics of Polyatomic Molecules in Laser Fields" | |

02 December 2013 | Andrew Huxley Edinburgh University | "Superconductivity and modulated states close to ferromagnet quantum critical points" | |

12 December 2013 | David A. Weitz Harvard University | "Fluctuations and stiffness of cells" |

date | speaker | title | |
---|---|---|---|

13 February 2012 | Andrew G. GreenLondon Centre of Nanotechnology | "New Horizons in Quantum Criticality" | |

26 March 2012 | Arthur VoterLos Alamos National Laboratory | "Recent Advances in Accelerated Molecular Dynamics Methods" | |

19 March 2012 | Roger GuimeraUniversitat Rovira i Virgili, Tarragona | "Statistical inference for the discovery of hidden interactions in complex networks" | |

02 April 2012 | Yoshinori TokuraThe University of Tokyo | "Emergent electromagnetic phenomena from topological spin textures" | |

16 April 2012 | Luis SilvaInstituto de Plasmas e Fusão Nuclear Complexo Interdisciplinar, Lisbon | "Intense lasers in plasmas: from accelerators to relativistic shocks" | |

23 April 2012 | Holger StarkTU Berlin | "Active motion in the microscopic world: From swinging and tumbling to bacterial locomotion" | |

21 May 2012 | Hidenori TakagiRIKEN, Japan | "Emergent phases of correlated electrons in transition metal oxides" | |

14 May 2012 | Albert-László BarabásiNortheastern University, Boston | "Network Science: From Structure to Control" | |

18 June 2012 | Joaquim PintoUniversität zu Köln | "Extreme events, climate change and related impacts" | |

25 June 2012 | Hari C. ManoharanDepartment of Physics, Stanford University | "Molecular Graphene" | |

02 July 2012 | Boris Altshuler | Martin Gutzwiller Fellowship, Award Ceremony "Anderson Localization – looking forward." | |

09 July 2012 | Dmitri TalapinThe University of Chicago | "The evolution of nanomaterials - From fundamental science to practical applications" | |

16 July 2012 | Ruth Nussinov Center for Cancer Research, Frederick, USA | "Networks in the Cell: Structural networks of signaling pathways on the proteome scale" | |

30 July 2012 | Gil RefaelCaltech | "Messy magnets and dirty superfluids" | |

13 August 2012 | Phil HodgkinThe Walter and Eliza Hall Institute of Medical Research and Ken DuffyNational University of Ireland | "Reverse engineering the immune system" | |

08 October 2012 | Steve GervinYale University | "Quantum Measurements and Back-Action (Spooky and Otherwise)" | |

29 October 2012 | Tomas BohrTechnical University of Denmark | "Spontaneous Symmetry Breaking on Fluid Surfaces" | |

12 November 2012 | F. Duncan M. HaldanePrinceton University | "Entanglement, Topology and Geometry in the Fractional Quantum Hall Fluid" | |

19 November 2012 | Constantino TsallisCentro Brasileiro de Pesquisas Fisicas, Rio de Janeiro | "Nonadditive entropy and applications in natural, artificial and social complex systems" | |

26 November 2012 | Robin SantraCFEL Hamburg | "Ultrafast x-ray atomic physics" | |

10 December 2012 | Marc TimmeMPI Göttingen | "Braess Paradox, (In-)Stability and Optimal Design: Network Dynamics of Modern Power Grids" |

date | speaker | title | |
---|---|---|---|

14 February 2011 | Harald EngelTU Berlin | "Wave nucleation in excitable media" | |

21 February 2011 | Klaus KroyUniversität Leipzig | "Hot Brownian Motion" | |

28 February 2011 | Ali YazdaniPrinceton University | "Helical Metals on the Surfaces of Topological Insulators" | |

21 March 2011 | Ben SimonsCambridge University | "Universalities of stem cell fate in adult tissues" | |

28 March 2011 | Victor GurarieUniversity of Colorado | "Non-Abelian particles in a two dimensional world" | |

04 April 2011 | Andreas RadbruchDeutsches Rheuma-Forschungszentrum, Berlin | "Modelling and experimentation: Approaching the complexity of the immune system" | |

11 April 2011 | Peter JungOhio University | "How nerves get into shape" | |

18 April 2011 | Qimiao SiRice University | "Quantum Criticality and Emergent Phases" | |

02 May 2011 | Ulrike FeudelCarl von Ossietzky Universität Oldenburg | "Patterns in the ocean resulting from the interplay between hydrodynamics and biology" | |

09 May 2011 | Fred WolfMax-Planck-Institut für Dynamik und Selbstorganisation | "The self-organization and quantitative universality in the evolution of the visual corte" | |

16 May 2011 | Chandra Varma University of California, Riverside | "What determined T_c in Superconductors through Pairing by Electronic Fluctuations" | |

06 June 2011 | Piers ColemanRutgers University | "Magnetism and Superconductivity: A new era of convergence in condensed matter physics." | |

20 June 2011 | Wolfgang SchleichUniversität Ulm | "The linearity of quantum mechanics and the birth of the Schroedinger equation" | |

27 June 2011 | Cristián HuepeUnaffiliated Research Scientist, Chicago | "Dynamics of collective motion: from toy models to experiments" | |

04 July 2011 | Felix von OppenFU Berlin | "Making and manipulating Majorana fermions for topological quantum computation" | |

11 July 2011 | Satya MajumdarUniversité Paris-Sud | "The Wonderful World of Brownian Functionals" | |

01 August 2011 | Joseph KlafterTel Aviv University | "How strange is strange kinetics" | |

12 September 2011 | Igor AronsonArgonne National Laboratory | "Active Magnetic Colloids: From Self-Assembled Swimmers to Simple Robots" | |

10 October 2011 | Herschel RabitzPrinceton University | "Control of phenomena in the sciences over vast length and time scales " | |

24 October 2011 | Albert FertUnité Mixte de Physique CNRS/Thales | "Graphene, carbon nanotubes and spintronics " | |

07 November 2011 | Alfred R. OsborneUniversità degli Studi di Torino | "Rogue Waves and Holes in the Sea" | |

21 November 2011 | Robert MoshammerMPI für Kernphysik Heidelberg | "Time-Resolved Experiments with Atoms and Molecules using XUV and IR Laser Pulses" | |

16 December 2011 | Ioannis Kevrekidis | Martin Gutzwiller Fellowship, Award Ceremony"Equation-Free and Variable-Free: a computer-assisted approach to modeling complex systems" |

date | speaker | title | |
---|---|---|---|

11 January 2010 | Werner KrauthEcole Normale Supérieure, Laboratoire de Physique Statistique, Paris | "'Perfect' sampling: a new paradigm for Monte Carlo calculations in statistical physics" | |

25 January 2010 | Eugenia Kalnay University of Maryland | "Use of breeding to find the physical causes of instabilities" | |

01 March 2010 | Hao TjengMax Planck Institute for Chemical Physics of Solids, Dresden | "Electron spectroscopy on 3d^1 transition-metal oxides: model studies for testing new theoretical approaches" | |

08 March 2010 | Maria Carmen RomanoUniversity of Aberdeen | "Traffic dynamics of translation: modelling the synthesis of proteins" | |

15 March 2010 | Hans von StorchInstitute for Coastal Research, GKSS Research Center, Geesthacht | "Utility of Climate Models" | |

29 March 2010 | Kirill ShtengelUniversity of California, Riverside | "Non-Abelian anyons: New particles for less than a billion" | |

12 April 2010 | Erwin FreyLudwig-Maximilians-Universität München | "Bacterial Games: on the role of space and stochasticity in coevolutionary dynamics" | |

26 April 2010 | Klaus MeckeUniversität Erlangen-Nürnberg | "Minkowski Tensors: linking physics and geometry of materials" | |

03 May 2010 | Ulrich SchollwöckLudwig-Maximilians-Universität München | "Playing with Superlattices: Ultracold Atoms out of Equilibrium" | |

10 May 2010 | Günther HasingerMax-Planck-Institut für Plasmaphysik | "The way to a fusion power station" | |

25 May 2010 | Gertrud ZwicknaglTU Braunschweig | "The f-electron's 'double life'" | |

31 May 2010 | Martin van Hecke Universiteit Leiden | "Flow of Foams from a Jamming Perspective" | |

07 June 2010 | Philip KimColumbia University | "Relativistic quantum physics at the tip of your pencil: pseudo spins in graphene" | |

14 June 2010 | Ian AffleckUniversity of British Columbia | "The Kondo screening cloud: what it is and how to observe it" | |

21 June 2010 | Paul Fendley University of Virginia | "From Few to Many" | |

28 June 2010 | Florin Diacu University of Victoria | "Collision and near-collision dynamics in various n-body problems" | |

05 July 2010 | Luca PelitiUniversità di Napoli "Federico II" | "Fluctuation relations in physical biology" | |

12 July 2010 | Carlo BeenakkerLeiden University | "Majorana fermions in topological insulators" | |

26 July 2010 | Götz S. UhrigTechnische Universität Dortmund | "Coherent Control of Quantum Bits: Ideas against Decoherence" | |

09 August 2010 | Serge Aubry | Martin Gutzwiller Fellowship, Award Ceremony"Different aspects of the localization of waves by disorder, nonlinearity and else... a short review" | |

16 August 2010 | Silke OspelkausMPI für Quantenoptik | "Ultracold Polar Molecules - Ultracold Chemistry and Dipolar Collisions" | |

23 August 2010 | Subir SachdevHarvard University | "The phase diagrams of the high temperature superconductors" | |

30 August 2010 | Klaus SengstockInstitut für Laser-Physik, Hamburg | "Ultracold Quantum Gases in Hexagonal Optical Lattices" | |

06 September 2010 | Gerald GabrielseHarvard University | "Fundamental Physics with Low Energy Particles of Antimatter and Matter" | |

13 September 2010 | Sabine Sütterlin Journalist in Residence | "What is it that journalists want from scientists?" | |

20 September 2010 | Kurt KremerMPI für Polymerforschung | "Multiscale Modelling of Soft Matter" | |

27 September 2010 | Michael HastingsMedical Research Council, Laboratory of Molecular Biology | "Pacemaking and synchronisation in the brains circadian centre, the suprachiasmatic nucleus" | |

04 October 2010 | Wieslaw Krolikowski The Australian National University | "Nonlocal Solitons" | |

11 October 2010 | Mehran KardarMassachusetts Institute of Technology | "Manipulating Fluctuation-Induced Forces" | |

25 October 2010 | Fabrizio GabbianiBaylor College of Medicine, Houston, TX | "Biophysics and Neural Computations Underlying Collision Avoidance Behaviors" | |

01 November 2010 | Roland Ketzmerick TU Dresden | "How fast can one tunnel into chaos?" | |

08 November 2010 | Raymond Goldstein University of Cambridge | "Microfluidics of Cytoplasmic Streaming" | |

22 November 2010 | Reinhard DörnerUniversität Frankfurt am Main | "The Helium Dimer: Double ionization by photons" | |

29 November 2010 | Jorge M. PachecoUniversidade do Minho, Universidade de Lisboa | "Evolutionary dynamics of Climate Change under the Collective Risk Dilemma" |

date | speaker | title | |
---|---|---|---|

12 January 2009 |
| "Optics in curved space" | |

19 January 2009 | Bruno EckhardtUniversität Marburg | "Turbulence transition in pipe flow and other shear flows" | |

26 January 2009 | Alexander HartmannUniversität Oldenburg | "Simulation of rare events" | |

09 February 2009 | David A. WeitzHarvard University | "Mechanics of biopolymer networks" | |

23 February 2009 | Royce K.P. ZiaVirginia Polytechnic Institute & State University | "Non-equilibrium statistical mechanics: A growing frontier of "pure and applied" theoretical physics" | |

02 March 2009 | Andrea CavalleriUniversity of Hamburg | "Photo-control in complex solids" | |

09 March 2009 | Walter HofstetterUniversität Frankfurt | "Disorder and interaction in optical lattices" | |

16 March 2009 | Thierry GiamarchiUniversity of Geneva | "Dirty bosons and cold atomic gases" | |

30 March2009 | Andrei Varlamov Università di Roma | "Giant Nernst effect due to fluctuating cooper pairs in superconductors" | |

06 April 2009 | Olivier PouliquenPolytech Marseille | "Granular flows: From aerial to submarine avalanches" | |

20 April 2009 | Klaus GerwertRuhr-Universität Bochum | "Proteins in action: Monitored by tr(time-resolved) FTIR spectroscopy" | |

27 April 2009 | Christoph BruchMax Planck Digital Library (MPDL) | "Will 'open access' change scientific publishing?" | |

04 May 2009 | Yuriy A. KosevichSemov Inst. of Chemical Physics, Russian Academy of Sciences | "Bloch acceleration theorem and Bloch oscillations in complex electronic, acoustic and magnetic systems" | |

11 May 2009 | Nadrian SeemanNew York University | "Using DNA information to control structure of matter in 3D" | |

18 May 2009 | Jean Zinn-JustinCEA Saclay | "Renormalization group approach to matrix models" | |

25 May 2009 | Joshua JortnerTel Aviv University | "Economic Engineering" | |

15 June 2009 | Achim WambachUniversitä:t zu Köln | "Adventures in the ultracold world" | |

08 June 2009 | Marcus AnhäuserJournalist in Residence 2009 | "Science journalism: What is it all about?" | |

22 June 2009 | Karl FristonUniversity College London | "Free-energy, perception and learning" | |

29 June 2009 | Dieter MeschedeUniversität Bonn | "Playing quantum marbles or can we make individual atoms interfere with each other?" | |

06 July 2009 | Hans Peter BüchlerUniversität Stuttgart | "Strongly correlated quantem phases with cold polar molecules" | |

15 July 2009 | Michael FreedmanMicrosoft Research | "Topology, physics and complexity: The birthing of the quantum computer" | |

20 July 2009 | Alexander S. MikhailovFritz-Haber-Institut der MPG, Berlin | "Nonlinear relaxation properties of elastic networks and nonequilibrium dynamics of protein machines" | |

03 August 2009 | Sergey A. NikitovRussian Academy of Sciences, Moscow | "Magnonic crystals and magnetic metamaterials based on magnetic films - New types of magnetic functional materials: Overview and perspectives" | |

07 September 2009 | Gerhard G. Paulus Universität Jena | "Recent experiments in above-threshold ionization" | |

14 September 2009 | Eric J. HellerHarvard University | "Tunneling and Coherence in Few and Many Body Systems" | |

21 September 2009 | Juan M. R. Parrondo | Martin Gutzwiller Fellowship, Award Ceremony "Paradoxes in stochastic dynamics" | |

28 September 2009 | Robert W. CarpickUniversity of Pennsylvania | "New insights into dissipative processes: Damping, adhesion, friction, and wear at the nanometer and atomic scale" | |

05 October 2009 | Bernd KrauskopfUniversity of Bristol | "Numerical bifurcation analysis applied to systems with delay" | |

12 October 2009 | Hans-Otto WaltherUniversität Gießen | "State-dependent delays: Framework, results, open problems" | |

19 October 2009 | Florian MarquardtLudwig-Maximilians-Universität München | "Optomechanics - The interaction between light and mechanical motion" | |

26 October 2009 | Judith FrydmanStanford University | "Molecular Origami: Protein folding and misfolding in health and disease" | |

02 November 2009 | Rob PhillipsCalifornia Institute of Technology | "Bacteria Are Stressed Out Too: The Physical Basis of Mechanosensation" | |

03 November 2009 | Wolf SingerMPI für Hirnforschung | "Distributed processing and temporal codes in cortical networks" | |

09 November 2009 | Eshel Ben-JacobTel Aviv University | "Chips of Hope: NeuroElectronic Hybrids for Brain Repair and Cognitive Machines" | |

16 November 2009 | Dean AstumianUniversity of Maine | "Thermodynamics and kinetics of molecular motors" | |

23 November 2009 | Peter AbbamonteUniversity of Illinois | "Why isn't graphene a strongly correlated electron system? - Insights from x-ray attosecond imaging" | |

30 November 2009 | Vladimir TikhonchukUniversité Bordeaux | "Physics of laser-assisted ion acceleration" | |

07 December 2009 | Andreas EngelUniversität Oldenburg | "Non-equilibrium work and fluctuation theorems" | |

14 December 2009 | Pierre SensLaboratoire de Physico-Chimie Théorique, CNRS-ESPCI, Paris | "Membrane-cytoskeleton interactions and mechanical regulation at the cell interface" |

date | speaker | title | |
---|---|---|---|

07 January 2008 | Hiroki SayamaBinghamton University, SUNY, USA | "Self-organizing structures and behaviors of heterogeneous self-propelled particle swarm models" | |

21 January 2008 | Jascha ReppUniversität Regensburg | "Current-induced conductance switching of individual molecules" | |

28 January 2008 | Achim RichterTU Darmstadt | "Playing billiards with microwaves - Quantum manifestations of classical chaos" | |

18 February 2008 | Charles MarcusHarvard University | "Schrödinger's Chip: Semiconductor approaches to quantum information" | |

31 March 2008 | Mahir S. Hussein | Martin Gutzwiller Fellowship, Award Ceremony"Role of chaos in the collective response of atom clusters and nuclei" | |

07 April 2008 | Albrecht Ott | "Criticality and spontaneous symmetry breaking are part of Hydra's developmental program for axis definition" | |

14 April 2008 | Michael BerryUniversity of Bristol | "Tsunami asymptotics" | |

21 April 2008 | Roland NetzTechnische Universität München | "Protein adhesion, friction and unfolding: Theoretical approaches" | |

28 April 2008 | Jeroen van den BrinkUniversiteit Leiden | "Novel routes to Multiferroics" | |

05 May 2008 | Guido CaldarelliUniversity of Rome | "Self-organized network evolution coupled to extremal dynamics" | |

19 May 2008 | Marileen Dogterom AMOLF Amsterdam | "Interaction of dynamic microtubule ends with 'cortical' dynein in vitro" | |

26 May 2008 | Udo SeifertUniversität Stuttgart | "Stochastic thermodynamics" | |

02 June 2008 | Carsten HonerkampUniversität Würzburg | "Lifestyles of the small and simple - exploring the world of interacting lattice fermions" | |

09 June 2008 | Raymond ShawPennsylvania State University | "Several unsolved problems in the physics of atmospheric clouds" | |

17 June 2008 | Laurens MolenkampUniversität Würzburg | "Quantum spin Hall effect" | |

23 June 2008 | Alan TennantHahn-Meitner-Institut Berlin | "Magnets as model systems - why simpler is better" | |

30 June 2008 | Piers ColemanRutgers University | "Qu-transitions. Phase transitions in the quantum era" | |

07 July 2008 | Manfred SigristETH Zürich | "How to form Cooper pairs without inversion symmetry?" | |

14 July 2008 | Falk LedererUniversität Jena | "Shaping light in structured materials" | |

21 July 2008 | Uri BaninHebrew University of Jerusalem | "Hybrid metal-semiconductor and semiconductor-semiconductor nanoparticles: From architecture to function" | |

28 July 2008 | Kevin BasslerUniversity of Houston | "The evolution of networks of competing Boolean nodes" | |

04 August 2008 |
| "Stimulated cooperative dynamics in complex solids" | |

18 August 2008 | Ulrich WeissUniversity of Stuttgart | "Decoherence and relaxation of coupled qubits" | |

01 September 2008 | Paul ChaikinNew York University | "Toward self-replication with colloids" | |

22 September 2008 | Eberhard BodenschatzMPI für Dynamik und Selbstorganisation | "Taming electrophysiological turbulence of the heart" | |

15 September 2008 | Martin MaxeyBrown University, Providence (USA) | "Active particle suspensions: Inertial particles in turbulence to micro-swimmers" | |

06 October 2008 | Fred MacKintoshVrije Universiteit Amsterdam | "Non-equilibrium mechanics and fluctuations in the cytoskeleton" | |

13 October 2008 | Nigel E. HusseyUniversity of Bristol | "Anisotropic scattering and anomalous criticality in high temperature superconductors" | |

20 October 2008 | Peter WölfleUniversität Karlsruhe | "The Kondo effect: From magnetic alloys to nanoelectronics" | |

27 October 2008 | Andreas BauschTechnische Universität München | "Cytoskeletal mechanics: Structure and dynamics" | |

03 November 2008 | Qian NiuUniversity of Texas | "Berry phase effects on spin and charge transport" | |

10 November 2008 | Frédéric MilaEcole Polytechnique Fédérale de Lausanne | "Exploring the physics of lattice bosons with quantum magnets" | |

24 November 2008 | John S BriggsUniversität Freiburg | "Max Born's legacy to quantum mechanics: From entanglement to quantum gravity" | |

17 November 2008 | Alois LoidlUniversität Augsburg | "Frustrated lattices in spinel compounds" | |

01 Dezember 2008 | Martin WolfFreie Universität Berlin | "Ultrafast dynamics of correlated electron systems" | |

08 December 2008 | Martin HolthausUniversität Oldenburg | "Near-field scanning thermal microscopy" | |

15 December 2008 | Nicolas BrunelCNRS, Université Paris | "Optimizing information storage in neural circuits: Consequences on the statistics of synaptic connectivity" |

date | speaker | title | |
---|---|---|---|

15 January 2007 | Manolis AntonoyiannakisAmerican Physical Society | "Peer Review at the journals of Physical Review & Letters" | |

12 February 2007 | Stefan BlawidQimonda Dresden GmbH & Co. | "Lithography simulations: Enabling leading-edge manufacturing of integrated semiconductor circuits" | |

19 February 2007 | Gregor TannerThe University of Nottingham | "The three-body Coulomb problem: Two electron atoms and the quantum mechanics of three-body collisions and chaos" | |

26 February 2007 | Wolfgang BelzigUniversität Konstanz | "Super-Spintronic" | |

12 March 2007 | Hans KrohaUniversität Bonn | "Transport theory of random laser" | |

26 March 2007 | Mordechai SegevTechnion Haifa | "Linear and nonlinear waves in photonic lattices: From lattice solitons to photonic quasecrystals, conical diffraction, and Anderson localization" | |

02 April 2007 | Miron AmusiaThe Hebrew University Jerusalem | "Many-electron atoms as complex systems" | |

23 April 2007 | Alexander LichtensteinUniversität Hamburg | "Prospects of realistic ARPES theory for correlated systems" | |

14 May 2007 | Steven L. Tomsovic | Martin Gutzwiller Fellowship, Award Ceremony "An irreversibility paradox in simple chaotic systems" | |

21 May 2007 | Hiroshi Katayama-YoshidaOsaka University | "Computational nano-materials design for semiconductor spintronics" | |

18 June 2007 | Eytan DomanyWeizman Institute of Science, Rehovot | "Predicting outcome in cancer: Hope, hype, physics and ... biology" | |

25 June 2007 | Patricio LeboeufUniversité Paris-Sud | "Interacting bosons in random media: Superfluidity versus Anderson localization" | |

02 July 2007 | Lutz Schimanskyl-GeierHumboldt Universität zu Berlin | "Coupled noisy oscillators" "Coupled noisy oscillators" | |

23 July 2007 | Nilanjana Datta University of Cambridge | "Perfect transfer of quantum information" | |

30 July 2007 | Andrey V Chubukov The University of Wisconsin | "Non-analyticities in the thermodynamics of Fermi liquids" | |

20 August 2007 | David Goldhaber-GordonStanford University | "Designer Hamiltonians in the laboratory: Observation of many-body physics in a semiconductor nanostructure" | |

01 October 2007 | Martin HeisenbergUniversität Würzburg | "Localized engrams and models of memories in flies" | |

29 October 2007 | Andreas Buchleitnermpipks | "Open Systems (Dis-)Entanglement: What we know, and what we would like to know" | |

05 November 2007 | Ken LedinghamUniversity of Strathclyde, Glasgow | "A vision for laser induced particle acceleration and applications" | |

12 November 2007 | Kazimierz RzazewskiPolish Academy of Sciences and University Warsaw | "Bose statistics revisited" | |

19 November 2007 | André D. BandraukUniversité de Sherbrooke, Quebec, Canada | "Attosecond molecular physics. The next frontier" | |

26 November 2007 | Hanspeter HelmUniversität Freiburg | "Electric field effects in Rydberg states of triatomic hydrogen" | |

10 December 2007 |
| "Fluid dynamics and the evolution of biological complexity" | |

17 December 2007 | Dirk BrockmannMPI für Dynamik und Selbstorganisation, Göttingen | "New perspectives on global human traffic, scaling laws and emergent geographic communities" |

date | speaker | title | |
---|---|---|---|

23 January 2006 | William J. FirthUniversity of Strathclyde, Glasgow | "Cavity Solitons: Creation, Control, Complexes" | |

13 February 2006 | Zoltan ToroczkaiLos Alamos National Laboratory | "Conformation networks: An application to protein folding" | |

27 February 2006 | Michael GhilENS Paris and University of California, Los Angeles | "The Earth as a Complex System, and a Simple Way of looking at it" | |

20 March 2006 |
| "Magnetic field dependence of ht dielectric function of glasses" | |

24 April 2006 | Georgy ShlyapnikovUniversité Paris-Sud | "Strongly interacting ultracold Fermi gases" | |

02 May 2006 | Warren PickettUniversity of California, Davis | "Strong coupling superconductivity: Paradigm shifts, alternative universes | |

22 May 2006 | Richard WebbUniversity of South Carolina, USA | "Shot noise and decoherence in nanostructures" | |

29 May 2006 | Pierre MeystreUniversity of Arizona, Tuscon | "Nonlinear optics of atoms and molecules" | |

12 June 2006 | Lawrence S. Schulman | Martin-Gutzwiller-Fellowship, Award Ceremony "Imaging dynamics: Phase transition, clusters, and geometry from spectral analysis" | |

13 June 2006 | Walter HofstetterUniversität Frankfurt | "Strong correlations in ultracold atoms" | |

19 June 2006 | Lakshminarayanan MahadevanHarvard University | "Mechanics and mobility" | |

26 June 2006 | Roderich MoessnerCNRS and ENS Paris | "Frustration, liquidity and exotic order" | |

11 July 2006 | Felix von OppenFU Berlin | "Molecular electronics - Technology or physics?" | |

17 July 2006 | Peter HänggiUniversität Augsburg | "The ring of Brownian motion for complexity: Past, presence and future" | |

24 July 2006 | Luiz DavidovichRio de Janeiro | "Entanglement and decoherence" | |

31 July 2006 | Joerg SchmiedmayerUniversität Heidelberg | "Interference and coherence in 1-d Bose-Einstein-Condensates" | |

14 August 2006 | Leonid GlazmanUniversity of Minnesota | "Inelastic electron scattering off magnetic impurities" | |

18 September 2006 | Vladimir FalkoLancaster University | "Introduction to the two dimensional electron physics of graphene (monolayers and bilayers of graphite)" | |

25 September 2006 | Helmut RauchAtominstitut der Österreichischen Universitäten, Vienna | "Quantum phenomena observed by neutron interferometry" | |

02 October 2006 | Klaus von KlitzingMPI Stuttgart | "Quantum-Hall-Effect and Metrology" | |

09 October 2006 | Guillaume LabeyrieInstitut Non Linéaire de Nice | Multiple scattering of light in cold atoms | |

23 October 2006 | Pawel HorodeckiGdansk University of Technology | "Quantum entanglement phenomenon and quantum communication" | |

06 November 2006 | Jaroslav FabianUniversität Regensburg | "Perspectives in spintronics" | |

13 November 2006 | Frans A. SpaepenHarvard University | "Colloidal Systems: 'Analog computers' for simulating the dynamics of crystals and glasses" | |

27 November 2006 | Alexander PukhovUniversität Düsseldorf | "Electron acceleration in the bubble regime" | |

04 December 2006 | David M. LeitnerThe University of Nevada | "Molecules through the mesoscope" | |

11 December 2006 | Georg MaretUniversität Konstanz | "Anderson-localization of light" | |

18 December 2006 | Han WoerdmanLeiden University | "Entangled photons" |

date | speaker | title | |
---|---|---|---|

12 January 2004 | Jörg P. KotthausLMU Müchen | "Juggling electrons in artificial potentials" | |

26 January 2004 | Edouard Brézin E.N.S. Paris | "Various uses of random matrices" | |

09 February 2004 | H. G. Schuster Universität Kiel | "Adaptation and control in competitive games" | |

23 February 2004 | Mark ReedYale University | "A decade of molecular electron transport" | |

02 March 2004 | Uzy SmilanskyWeizmann Institute Rehovot | "Computational Archeology" | |

05 April 2004 | Christian Beck University of London | "Superstatistics: Theory and Applications" | |

19 April 2004 | Friedrich WagnerMPI für Plasmaphysik Garching, Greifswald | "Progress in Fusion Research" | |

03 May 2004 | Dan KleppnerMassachusetts Institute of Technology, Cambridge | "Rydberg atom physics: The history of a subfield" | |

10 May 2004 | Michel BruneE.N.S. Paris | "Entanglement, quantum measurement and quantum information with Rydberg atoms and cavities" | |

17 May 2004 | Kurt WiesenfeldGeorgia Institute of Technology, Atlanta | "Stochastic Resonance: Past progress and open questions" | |

24 May 2004 | Roman SchnabelUniv. Hannover, MPI für Gravitationsphysik Hannover | "Gravitational wave detectors: Today and in future" | |

01 June 2004 | Jürgen KurthsUniversität Potsdam | "Synchronization phenomena in systems with complicated topology" | |

07 June 2004 | Wolfgang NoltingHumoldt-Universität zu Berlin | "Ferromagnetism: An indestructible hot topic" | |

08 June 2004 | Ulrich SchollwoeckRWTH Aachen | "Simulating the time-evolution of strongly correlated quantum systems" | |

14 June 2004 | Boris ShklovskiiUniversity of Minnesota | "Fractionalization induced charge inversion of DNA and gene therapy" | |

21 June 2004 | Maya PaczuskiImperial College London | "Scale-free magnetic networks: Empirical results and a self-organizing model of the coronal field" | |

05 July 2004 | Peter SchusterUniversität Wien | "The indispensibility of neutrality in molecular evolution" | |

12 July 2004 | Celso GrebogiUniversidade de Sao Paulo | "Fractal skeletons and the plankton paradox" | |

19 July 2004 | Italo GuarneriUniversity Como, Italy | "New and old aspects of nonlinear dynamics unveiled by experiments of cold-atoms optics" | |

26 July 2004 | Stefan LudingTU Delft | "Statistical physics meets mechanics: Structures and pattern formation in granular systems" | |

02 August 2004 | Wolfgang LangeMPQ Garching | "Deterministically engineered single photons from a single ion" | |

23 August 2004 | Eshel Ben-JacobTel Aviv University | "Why bacteria go complex - Higher flexibility for better adaptability" | |

30 August 2004 | Henning SamtlebenUniversität Hamburg | "Masses and symmetries from extra dimensions" | |

27 September 2004 | David QuéréCollege de France, Paris | "Slippery textured surfaces" | |

04 October 2004 | Fabio MarchesoniUniversity of Camerino, Italy | "Stochastic Resonance" | |

11 October 2004 | G. V. Shlyapnikov Université de Paris-Sud | "Dynamics of solitons in Bose-condensed gases" | |

18 October 2004 | Immanuel BlochUniversität Mainz | "Seeing the particles beneath the waves - Beyond mean field physics with Bose-Einstein condensates in optical lattices" | |

25 October 2004 | Daniel Esteve SPEC CEA-Saclay, France | "Control and decoherence of a quantum bit circuit" | |

08 November 2004 | Siegfried GrossmannUniversität Marburg | "Boundary layer physics" | |

15 November 2004 | Alexander HolevoMoscow University | "Classical and quantum information: Randomization and entanglement" | |

22 November 2004 | Jochen GemmerUniversität Osnabrück | "From quantum mechanics to thermodynamics?" | |

29 November 2004 | Gerard MeijerFritz-Haber-Institut der MPG, Berlin | "Manipulation of molecules with electric fields" | |

13 December 2004 | Rüdiger WehnerUniversity Zürich | "Desert ant navigation: mini-brains - mega tasks - smart solution" | |

| |||

17 January 2005 | Massimo InguscioUniversity of Florence, Italy | "Quantum degenerate atomic gases in ordered and disordered potentials" | |

07 February 2005 | Karl LeoTU Dresden | "Organic semiconductors: Physics and device applications" | |

14 February 2005 | Diederik S. Wiersma LENS Florence, Italy | "Light in and from complex photonic materials" | |

21 February 2005 | Hans J. Herrmann Universität Stuttgart | "Fragmentation" | |

28 February 2005 | Volker MedenUniversität Göttingen | "Transport in quantum wires: Inhomogeneities, correlations, and future nano-electronics" | |

04 April 2005 | Michael Norman Argonne National Laboratory | "Pseudogaps, strange metals, and coherent superconductors: The view from ARPES" | |

11 April 2005 | David NelsonHarvard University | "DNA unzipping and motor proteins: Effect of the genetic code" | |

18 April 2005 |
| Martin-Gutzwiller-Fellowship, Award Ceremony "Dynamics of high-dimensional systems: from a microscopic to a macroscopic description" | |

25 April 2005 | Ignacio CiracMPQ Garching | "Simulation of quantum many-body systems" | |

02 May 2005 | Ennio ArimondoUniversitá di Pisa | "Experiments with Bose-Einstein condensates within optical lattices" | |

30 May 2005 | Hans-Peter HerzelHU Berlin | "Feedbacks, oscillations and synchronization in mammalian cells" | |

06 June 2005 | Abraham NitzanTel Aviv University | "Inelastic effects in electron tunneling" | |

13 June 2005 | Eberhard GrossFU Berlin | "Time-dependent density functional theory: Basic concepts and new developments" | |

20 June 2005 | MPI of Neurobiology, MartinsriedAlexander Borst | "Adaptation without parameter change: Automatic gain control in Reichardt-type motion detectors" | |

27 June 2005 | Alain ArneodoENS Lyon | "DNA in chromatin: What can we learn from a multi-scale wavelet analysis of DNA sequences" | |

04 July 2005 | Alessandro de MouraUniversidade de Sao Paulo | "Tunneling and non-hyperbolicity in quantum dots" | |

11 July 2005 | Leo van HemmenTU München | "Mechanosensory localization: What owls, frogs, and scorpions have in common" | |

25 July 2005 | William G. UnruhUniversity of British Columbia, Vancouver | " Dumb Holes " | |

15 August 2005 | Pierre AgostiniCEA Saclay, France | "High harmonics attosecond chirp" | |

05 September 2005 | Robin HudsonLoughbourough | "Einstein's quantum, relativity and randomness: A centennial triple fugue" | |

19 September |
| "Einstein and quantum mechanics: Are wave functions of individual particles for real?" | |

26 September 2005 | Maciej LewensteinBarcelona | "Quo vadis optica quantorum?" | |

17 October 2005 | Dario BressaniniUniversitá dell'Insubria, Como | "The fascinating Helium Atom" | |

07 November 2005 | Hendrik J. Monkhorst University of Florida | "Chemistry, Physics and the Born-Oppenheimer Approximation" | |

28 November 2005 | Angel Rubio Universidad del Pais Vasco, San Sebastian/Donostia | "Response functions from a TDDFT-based formalism: Applications to low dimensional structures" | |

19 Dezember 2005 | William BialekPrinceton University | "Maximum entropy models for biological networks" |

date | speaker | title | |
---|---|---|---|

07 January 2002 | Shmuel FishmanIsrael Institute of Technology | "Relaxation and diffusion in chaotic systems" | |

14 January 2002 | Lorenz S. CederbaumUniversität Heidelberg | "Intermolecular Coulombic decay in clusters and weakly bound systems" | |

21 January 2002 | Jürgen Kuebler TU Darmstadt | "Magnetism of metals: a density functional view" | |

28 January 2002 | Christof WunderlichUniversität, Hamburg | "Thermally activated escape and stochastic resonance with individual atoms" | |

04 February 2002 | Rüdiger Kniep MPI CPfS | "Complexity in Chemistry: A + B = AB" | |

18 February 2002 | Kai Nagel ETH Zürich | "Breakdown and recovery in traffic flow models" | |

25 February 2002 | Andreas SchadschneiderUniversität zu Köln | "Cellular automaton approach to pedestrian dynamics" | |

04 March 2002 | James A. WarrenNIST, Gaithers Burg, MD | "Phase field modeling of crystal growth, grain boundaries and electrodeposition: A unified approach" | |

08 April 2002 | Jonathon Howard MPI CBG Dresden | "Microtubules, Motors and Mechanoreceptors" | |

15 April 2002 | Alfredo Ozorio d' Almeida MPIPKS | Martin-Gutzwiller-Fellowship, Award Ceremony "The birth of 'Semiclassics': A personal view of the Gutzwiller Trace Formula" | |

22 April 2002 | Arkady Pikovsky Universität Potsdam | "Synchronization" | |

29 April 2002 | Johannes Voit Dt. Sparkassen- und Giroverband | "From Brownian motion to operational risk: Physics and financial markets" | |

13 May 2002 | Giulio CasatiUniv. Como | "Efficient quantum computing of complex dynamcis" | |

27 May 2002 | R. LuestDt. Klimarechenzentrum Hamburg | "From the bottom of the sea, down to earth into space" | |

03 June 2002 | Antti-Pekka JauhoMicro- and Nanotechnology Research Center, Lyngby, Denmark | "Mesoscopic Coulomb drag" | |

10 June 2002 | Robert BrooksTechnion Haifa | "Spectral properties of Riemann surfaces" | |

17 June 2002 | Louis Kauffman University of Illinois, Chicago | "Knots and Physics" | |

24 June 2002 | Isabel Darcy University of Texas | "Tied in Knots: Applications of knot theory to the study of protein mechanism" | |

01 July 2002 | Sergey NovikovLandau Institute Moscow and University of Maryland | "Topological phenomena in normal metals" | |

15 July 2002 | Jörg Bilgram ETH Zürich | "Solidification far from equilibrium - Morphologies of xenon crystals | |

22 July 2002 | Alexander Grosberg University of Minnesota | "Physics of charge inversion in chemical and biological systems" | |

05 August 2002 | Pierre GaspardUniversite Libre de Bruxelles | "Microscopic chaos and transport phenomena" | |

12 August 2002 | Nicolai ChernovUniversity of Alabama | "Dynamics of a massive piston in an ideal gas" | |

19 August 2002 | Denis J. EvansAustralian National University | "The fluctuation theorem" | |

26 August 2002 | Michael MenzingerUniversity of Toronto | "Reactive Flows in Toronto" | |

23 September 2002 | Patrick Tabling ENS Paris | "Some physical and dynamical aspects in microfluid systems" | |

30 September 2002 | Manuel A. Fortes Universidade Tecnica de Lisboa | "Solid and liquid foams: Concepts and rheological properties" | |

07 October 2002 | Richard GillUniversity Utrecht | "Passion at a distance of 30 sigma?" | |

14 October 2002 | Bernhard Kramer University Hamburg | "Scaling at the Anderson transition" | |

21 October 20002 | Eric Clément Université Paris IV | "Fragility of granular matter: An experimentalist's point of view" | |

28 October 2002 | Michael E. Fisher University of Maryland | "The SAGA of COULOMBIC CRITICALITY: From Debye and Hückel to Ginzburg and beyond" | |

04 November 2002 | Hermann Grabert Universität Freiburg | "Electron-electron interactions in mesoscopic wires" | |

11 November 2002 | Eric J. HellerMPIPKS | "From quantum corrals to concert halls: Waves in confined spaces" | |

18 November 2002 | Ramamurti ShankarYale University | "Renormalization group for interacting fermions - a pedagogical introduction" | |

25 November 2002 | Beate SchmittmannVirginia Tech | "Driven diffusive systems: Surprises far from thermal equilibrium" | |

02 December 2002 | Clemens BechingerUniversität Konstanz | Colloidal suspensions as analog computers for complex tasks" | |

09 December 2002 | T.W. Haensch MPQ Garching | "Precision spectroscopy with ultra-short pulses" | |

| |||

13 January 2003 | Philippe BlanchardUniversität Bielefeld | "Complex random network: The origin of scale-free graphs, percolation, epidemic thresholds and all that" | |

20 January 2003 | Oriol BohigasLPTMS, Orsay | "Quantum chaos: From the atomic nucleus to the Riemann zeta function" | |

27 January 2003 | Nimrod MoiseyevTechnion Haifa | "NON HERMITIAN QUANTUM MECHANICS: Theory and applications to problems that hard/impossible to solve by the conventional QM" | |

03 February 2003 | Ingolf Volker HertelMax-Born-Institut Berlin | "Ultrafast dynamics and H-transfer in clusters and biologically relevant molecules" | |

10 February 2003 | Bruno Eckhardt University Marburg | "Chaotic mixing" | |

17 February 2003 | Ernst H. Brandt MPI for Metals Research Stuttgart | "Statics and dynamics of the vortex lattice in high-Tc superconductors" | |

24 February 2003 | Philipp GegenwartCPfS Dresden | "Quantum criticality in heavy Fermon systems" | |

17 March 2003 | T. Maurice RiceETH Zürich | "The diversity of electronic states in solids - A challenge for renormalization group methods" | |

07 April 2003 | Michael F. CrommieUniversity of California at Berkeley | "STM studies of surface Kondo impurities and clusters" | |

14 April 2003 | Matthias SteinmetzAstrophysikalisches Institut Potsdam (AIP) | "Structure formation in a preposterous universe" | |

28 April 2003 | Hans BriegelLMU München | "Multi-particle entanglement: Concepts and applications" | |

12 May 2003 | Marek PloscajczekGANIL Caen | "Description of the structure of weakly bound/unbound correlated quantum systems" | |

19 May 2003 | Werner HankeUniversität Würzburg | "Where are we at in the microscopic theory of high-T_{c} superconductivity?" | |

26 May 2003 | Raymond KapralUniversity Toronto | Martin-Gutzwiller-Fellowship, Award Ceremony "Knotty problems in nonlinear dynamics" | |

02 June 2003 | Julius WessLMU Müchen | "Field theory and quantum mechanics on deformed spaces" | |

10 June 2003 | A. K. WroblewskiWarsaw University | "Sense and nonsense in bibliometrics" | |

16 June 2003 | D. D. OsheroffStanford University | "The importance of interactions between TS in glassy materials at low temperatures: A historical perspective" | |

23 June 2003 | Daniel RobertUniversity of Bristol | "The ears of insects: Microscale sensors and auditory nanomechanics" | |

30 June 2003 | Andreas SchäferUniversität Regensburg | "Quantum chromodynamics and random matrix theory" | |

07 July 2003 | Frank CichosTU Chemnitz | "Diffusion in nanostructures" | |

17 July 2003 | Ian AffleckBoston University | "Conductance of Luttinger liquid y-junctions" | |

21 July 2003 | Ralf MetzlerNORDITA Copenhagen | "Topology matters: Some aspects of DNA physics" | |

04 August 2003 | Piet BrouwerCornell University Ithaka, USA | "Quantum pumps for charge and spin" | |

18 August 2003 | Klaus Dietz MPIPKS | "Quantum dynamics in open systems" | |

25 August 2003 |
| "Initializing at will: Equation-free modeling and experimentation" | |

06 October 2003 | Claude Godreche CEA Saclay | "Nonequilibrium dynamics of ferromagnetic spin systems" | |

20 October 2003 | A. J. HudspethThe Rockefeller University, New York | "Making an effort to listen: Mechanical amplification by novel molecular motors in the ear" | |

27 October 2003 | Rainer BlattUniversität Innsbruck | "Quantum computer - dream and realization" | |

03 November 2003 | Gerard t'HooftUtrecht University | "Quantum Mechanics at the Black Hole Horizon" | |

10 November 2003 | Hans-Jürgen StöckmannUniversität Marburg | "Transmission studies in open microwave billiards" | |

17 November 2003 | Gerhard BirklUniversität Hannover | "Atomic quantum systems in optical mircro-structures" | |

24 November 2003 | Heiner IgelLMU München | "Computational wave propagation in seismology" | |

01 December 2003 | Gerd LeuchsUniversität Erlangen-Nürnberg | "Quantum properties of optical fiber solitons" | |

08 December 2003 | Wolfgang ZinthLMU München | "Photosynthesis - ultrafast reactions for highly efficient energy conversion" | |

15 December 2003 | Michael HortmannUniversität Bremen | "Cryptography and quantum mechanics" |

date | speaker | title | |
---|---|---|---|

23 March 2000 | Todd DitmireLivermore | "Studies of intense laser driven Coulomb explosions in large clusters and applications to deuterium nuclear fusion" | |

17 April 2000 | Berthold-Georg EnglertUniversitaet Ulm und MPQ Garching: | "Quantitative Wave-Particle-Dualism" | |

08 May 2000 | I. MertigDresden | "Tunneling magneto-resistance: a new phenomenon?" | |

15 May 2000 | P. GrassbergerWuppertal | "Why it helps to be biased and opportunistic when doing simulations" | |

22 May 2000 | Eric HellerHarvard University | "Putting Quantum Phase Space to Work: From Chaos to Chemistry" | |

29 May 2000 | CeladaGenua | "Modelling the immune system and why" | |

05 June 2000 | Wilhelm ZwergerLMU München | "Topological effects and universal force oscillations in nanocohesion" | |

19 June 2000 | M. WilkensUniversity Potsdam | "Quantum Games" | |

03 July 2000 | R. N. MantegnaPalermo | "Physics of Stock Markets" | |

10 July 2000 | Achim WixforthCenter for NanoScience, LMU Muenchen | "Nano-Quakes on a Chip: Surface acoustic waves in semiconductor physics" | |

17 July 2000 | Ken TaylorBelfast | "Laser-driven 3-body Coulomb dynamics in atoms and molecules'' | |

24 July 2000 | H. Weidenmüller | ''Recent Developments in Random Matrix Theory'' | |

31 July 2000 | Detlef DuerrUniversitaet Muenchen | ''Bohmian Mechanics-Foundation of Quantum Mechanics'' | |

11 September 2000 | Dominique DelandeMPIPKS | "Beyond Periodic Orbit Theory and Random Matrix Theory in Atomic Physics'' | |

18 September 2000 | Guenter RadonsTU Chemnitz | ''Theoretical Physics meets Engineering: Nonlinear Dynamics of Waterjet Cutting'' | |

25 September 2000 | Gerd SchoenUniversitaet Karlsruhe | ''Josephson Qubits und der Quantenmessprozess'' | |

30 October 2000 |
| ''The Dictostelium Amoeba: A motion-dominated lifecycle'' | |

06 November 2000 | Michael SchreiberTU Chemmitz | ''Correlated Electrons in the Quantum Coulomb Glass and in Parabolic Quantum Dots'' | |

13 November 2000 | D. VollhardtUniv. Augsburg | ''Strongly Correlated Electron Systems: Problems, Progress and Perspectives'' | |

20 November 2000 | Peter LambropoulosUniversity of Crete | ''Two- and Three-Electron Atoms Driven by Laser Fields'' | |

27 November 2000 | Hans HerrmannUniv. Stuttgart | ''The form of dunes'' | |

05 December 2000 | Seth PuttermanUniversity of California | ''Sonoluminescence'' | |

11 December 2000 | Joachim HilgertTU Clausthal | ''Introduction to the Mathematical Problems of Quantum Chaos'' | |

18 December 2000 | Werner EbelingHumboldt-Universität Berlin | ''Complex Dynamics of Active Brownian Particles'' | |

| |||

08 January 2001 | Werner PeschUniversität Bayreuth | ''Spirals and Spiral Defect Chaos in Rayleigh-Benard Convection'' | |

15 January 2001 | Nicolas AgraitUniversidad Autonoma de Madrid | "Atomic Contacts and Atomic Chains" | |

22 January 2001 | Michael ThossTU München | "Semiclassical Description of Molecular Dynamics" | |

29 January 2001 | Dirk HelbingTU Dresden/Traffic Sciences | "Traffic and Other Self-Driven Many-Particle Systems" | |

05 February 2001 | Mathias BodeUniversity Münster and Cortologic AG Berlin | "Binocular Rivalry: On the Modelling of Decision Processes in the Visual Cortex" | |

12 February 2001 | Herbert WagnerLMU München | "Morphology of Large-Scale Structures in the Universe" | |

19 February 2001 | Oliver BensonUniversität Konstanz | "Novel Light Sources from Nanoparticles coupled to Microcavities: Quantum Optics on a Nanometer Scale" | |

26 February 2001 | Stephan DiekmannUniversität Jena | "Electrons in Biology - Structure and Function of Oxydoreductases" | |

12 March 2001 | David SherringtonUniversity Oxford | "Magnets, microchips, memories and markets: statistical physics of complex systems" | |

19 March 2001 | Martin RiedmillerUniversität Karlsruhe | "Reinforcement Learning in Cooperative Multi Agent Systems" | |

02 April 2001 | Richard PrangeMPIPKS | Martin-Gutzwiller-Fellowship, Award Ceremony "Special Eigenstates in Quantum Chaos" | |

09 April 2001 | Gert-Ludwig IngoldUniversität Augsburg | "Josephson Effect and Phase Fluctuations" | |

23 April 2001 | L. Schimansky-GeierHumboldt-Universität Berlin | "Noise in excitable systems" | |

30 April 2001 | Hans De RaedtUniversität Groningen | "If we would have a quantum computer what can we do with it?" | |

07 May 2001 | Konstantin EfetovRuhr-Universität Bochum | "Quantum Interference and Coulomb Interaction in Arrays of Tunnel Junctions" | |

14 May 2001 | Kurt BinderUniversität Mainz | "Monte Carlo Simulations of Surface - Induced Order and Disorder" | |

21 May 2001 | Gustav GerberUniversität Würzburg | "Optimal Control of Quantum Dynamics by Adaptive Femtosecond Pulse Shaping" | |

28 May 2001 | A. J. LeggettUniversity of Illinois | "Superfluidity, phase coherence and the new Bose-condensed alkali gases" | |

11 June 2001 | Carl DettmannUniversity of Bristol | "Perturbation theories of stochastic chaos" | |

18 June 2001 | Gero VoglHahn-Meitner-Institut Berlin | "Quantum interferences and atomic jumps in solids" | |

25 June 2001 | Peter HänggiUniversität Augsburg | "Brownian Motors" | |

02 July 2001 | Peter M. KochState University of New York | "Phase Control of Atomic Dynamics in Strong, Bichromatic Fields" | |

09 July 2001 | Rudolf FriedrichUniversität Stuttgart | "Analysis of Stochastic Systems with Applications in Turbulence, Traffic and Medicine" | |

16 July 2001 | Herbert WaltherMPQ Garching | "Quantum Phenomena of Single Atoms" | |

30 July 2001 | Roman KoteckyUniversität Prag | "Mathematics of phase transitions: from finite size effects to zeros of partition function" | |

31 July 2001 | Sergey GanichevUniversität Regensburg | "Conversion of spin into directed electric current in quantum wells" | |

17 September 2001 | Annette ZippeliusUniversität Göttingen | "Critical Dynamics of Gelation" | |

08 October 2001 | Turgay UzerAtlanta | "Rydberg Electron Dynamics in Many (>2) Degrees-of-Freedom" | |

15 October 2001 | Kestutis PyragasSemiconductor Physics Institute Vilnius, Lithuania | "Control of chaos via an unstable delayed feedback controller" | |

22 October 2001 | Jean DalibardLaboratoire Kastler Brossel Paris | "Bose-Einstein Condensates: Quantum Coherence and Superfluidity" | |

29 October 2001 |
| "Random light: From localization to random lasers" | |

05 November 2001 | Leonid P. Shilnikov Novgorod University | "Basic bifurcations of dynamical systems" | |

12 November 2001 | Siegfried HessTU Berlin | "Flow properties of complex fluids" | |

19 November 2001 | R. SauerbreyUniversität Jena | "Interaction of intense laser radiation with matter" | |

26 November 2001 | Uzy Smilansky Weizmann Institut | "Counting Nodal Domains - from Chladni to Quantum Chaos" | |

03 December 2001 | Eckehard Schöll TU Berlin | "Transport in nanostructures - a paradigm for complex nonlinear dynamics and pattern formation" |