Collisionless Transport Close to a Fermionic Quantum Critical Point in Dirac Materials
B. Roy et al., Phys. Rev. Lett. 121, 137601 (2018)
Dirac fermions are realized as low-energy excitations in a wide class of condensed matter systems, such as graphene and surface states of topological insulators. These so-called Dirac materials are rather stable against weak Hubbard-like local interactions. However, at strong interactions they may undergo quantum phase transitions into broken symmetry phases, such as spin- and charge-density-waves. The question then arises what may be the possible experimental imprints of such a quantum phase transition in terms of observable. Researcher from MPIPKS in collaboration with Nordita recently showed that the frequency-dependent electrical conductivity at both zero and finite temperature gets suppressed in the close vicinity to such critical point in comparison to its counterpart in a noninteracting system. Such peculiar, but universal behavior stems from strong interactions among wildly fluctuating gapless fermionic and bosonic order-parameter excitations inside the quantum critical regime, occupied by a relativistic non-Fermi liquid.
New Clusters of Excellence for the TU Dresden - The MPIPKS is part of two new Dresden clusters
The German Research Foundation (Deutsche Forschungsgemeinschaft) announced the new Clusters of Excellence in the framework of the Excellence Strategy of the German Federal and State Governments. The TU Dresden received three new Clusters of Excellence: "Physics of Life", "Center for Tactile Internet", and "Complexity and Topology in Quantum Materials" jointly with the University of Würzburg.
The Max Planck Institute for the Physics of Complex Systems is involved in two of the new Dresden Clusters: "Physics of Life" and “Complexity and Topology in Quantum Materials".
- "Physics of Life"
- “Complexity and Topology in Quantum Materials"
Global Phase Diagram of a Dirty Weyl Liquid and Emergent Superuniversality
B. Roy et al., Phys. Rev. X 8, 031076 (2018)
Weyl semimetals are exotic materials in which electrons behave more like photons - massless particles moving at a relativistic speed. However, it is unclear how well Weyl semimetals hold on to their bizarre properties in real disordered materials that are littered with impurities. Researchers from MPIPKS in collaboration with Nordita show that for small amounts of disorder such gapless topological semiconductors are stable, but at intermediate disorder these systems can undergo a quantum phase transition into a metallic phase, where electrons cease to behave as relativistic particles. Intriguingly, they discovered that the nature of this continuous transition is insensitive to the many (if not all) details of impurities, a phenomenon commonly referred to as superuniversality, which leaves its signature on the behavior of various observables, such as specific heat and electrical conductivity. These features combined with several other known transitions constitute the global phase diagram of disordered Weyl systems.
Resonance eigenfunction hypothesis for chaotic systems
K. Clauß et al., Phys. Rev. Lett. 121, 074101 (2018)
Classical systems with particles escaping through an opening are quantum mechanically described by resonance eigenfunctions. They are for example important for scattering experiments, like emission from optical microcavities, and show fractal patterns which strongly depend on their decay rate. The resonance eigenfunction hypothesis put forward in the paper provides a detailed understanding of this fractal structure. It is based on classical properties of the chaotic dynamics with a new time scale given by the temporal distance to the so-called chaotic saddle. Numerical support is presented for a chaotic map with escape.
Floquet Engineering of Optical Solenoids and Quantized Charge Pumping along Tailored Paths in Two-Dimensional Chern Insulators
Botao Wang et al., Phys. Rev. Lett. 120, 243602 (2018)
The adiabatic creation of single quasipartices or quasiholes via the insertion of one magnetic flux quantum through an infinitely thin solenoid is a famous gedanken experiment of quantum-Hall physics. In the present paper, physicists from Dresden show how this scenario can be realized in a real experiment with ultracold atoms in optical lattices. For this purpose, they propose a scheme for engineering "optical solenoids", tunable artificial magnetic fields piercing a single plaquette of an optical lattice. Moreover, they investigate how this technique can be used for quantized charge pumping along tailored paths in two dimensional topological Chern insulators.
Biophysicist Frank Jülicher elected for EMBO membership
Frank Jülicher, director of the Max Planck Institute for the Physics of Complex Systems (MPI-PKS) and the CSBD, is one of 62 outstanding life scientists, that have been elected to the European Molecular Biology Organization (EMBO). With his election, the biophysicist is joining a group of over 1800 EMBO researchers in Europe and around the world.
New Research Group: Computational Quantum Many-Body Physics
Welcome David Luitz! David heads the new research group
"Computational Quantum Many-Body Physics" which will study strongly
interacting quantum matter and in particular phenomena that arise due to
the presence of many particles. Using computational
many-body techniques such as exact diagonalization and tensor network
methods, both equilibrium and nonequilibrium properties of strongly
interacting quantum systems will be investigated, in particular in the
context of periodic driving, dissipation and strong disorder.
F. Mivehvar et al., Phys. Rev. Lett. 120, 123601 (2018)
Supersolids, a mysterious phase of matter consisting of a crystal which can flow without friction, have been elusive to experimental confirmation till last year, where the first realisations using ultracold atomic systems have been achieved. These atomic implementations however take place in driven-dissipative systems, a situation which lies outside the?thermal equilibrium scenario so far considered in theory.
In this work, we study for the first time the effect of the openness of the system on the main features of a supersolid, and find that its hallmarks can be robust against drive and dissipation whenever the latter preserve spatial translation invariance.
We are glad to announce the arrival of Dr. Christoph A. Weber, who heads the research group ‘Mesoscopic Physics of Life' since March 1, 2018. The group is interested in intra-cellular organisation and aims in particular to understand the role of phase transitions inside cells, including the impact of phase separation and protein aggregation during development and in the context of disease. Further interests are to unravel physical principles underlying the early formation of proto-cells at the origin of life.