Bust of Max Planck

Highlights

Publication Highlights

Live cell X-ray imaging of autophagic vacuoles formation and chromatin dynamics in fission yeast

Strelnikova et al., Scientific Reports 7, 13775 (2017)

The major challenge of X-ray imaging of living cellular specimens with a higher resolution than the optical resolution is the very low lethal radiation dose. Owing to the radiation damage and a low electron density contrast, sequential X-ray imaging of live cells was not possible so far. In our manuscript, we demonstrate the first X-ray movies of living yeast cells showing the dynamics of the autophagic vacuole formation and chromosome motion. It is a new way of seeing physiological processes of living organisms at nanoscale resolution. Moreover, the found lower lethal dose for dividing cells in comparison to non-dividing cells, might be an alternative approach to selective killing of malicious cells.
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Publication Highlights

Interaction Dependent Heating and Atom Loss in a Periodically Driven Optical Lattice

Martin Reitter et al., Phys. Rev. Lett. 119, 200402

Time periodic driving, for example in the form of coherent radiation, is a standard tool for the manipulation of small quantum systems like single atoms. With the advent of highly controllable and well isolated quantum gases of neutral atoms, periodic driving has recently become a powerful tool also for the coherent control of many-body systems. A milestone is the possibility to couple the motion of neutral atoms to artificial magnetic fields, which allows to study quantum Hall physics with atomic quantum gases. However, periodically driven many-body systems suffer from unwanted intrinsic heating, the time scale of which should be large compared to the duration of the experiment. In a joint work of Scientists from Munich, Cambridge and Dresden, the interaction dependence of such intrinsic heating has now been measured for the first time and compared to theory. Interestingly, for sufficiently large driving frequencies, heating was found to be reduced via a new form of evaporative cooling.
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Publication Highlights

High-temperature nonequilibrium Bose condensation induced by a hot needle

Alexander Schnell et al., Phys. Rev. Lett. 119, 140602

When a physical system is brought in weak thermal contact with an environment of temperature T, it will appproach an equilibrium state. The properties of this state depend on the temperature of the environment only. For example, a quantum gas of bosonic particles will form a Bose-Einstein condensate, where a macroscopic fraction the particles occupies the same state, below a condensation temperature T_c. In contrast, when a system is coupled to two heat baths of different temperatures T_1 and T_2, the situation changes in a fundamental way. In this case the system will assume a non-equilibrium steady state, which depends on the very details of both baths and not simply on their temperatures. It is an interesting question in how far this fact can be used to manipulate the far-from equilibrium state of the system in a controlled fashion by bath engineering. In this paper, we describe an astonishing effect: a Bose gas that is embedded in an environment of temperature T>>T_c can form a Bose condensate when coupled to a "hot needle", a second local bath of even larger temperature T_h>>T. Moreover, depending on the parameters and unlike in thermal equilibrium, the condensate can also be formed in an excited state of the system.
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Institute's News

New Research Group: Fractionalization and Topology in Quantum Matter

We welcome Inti Sodemann as new research group leader! The group will investigate a broad range of topics in quantum matter involving strong interactions, fractionalization, topology, and novel phenomena on spin and charge transport. The problems will be often inspired by experiments. One of the main goals is to develop new approaches to deal with strong interactions and fractionalization in gapless phases of matter.
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Publication Highlights

Observation of a dynamical quantum phase transition

Petar Jurcevic et al., PRL 119, 080501

Today, the equilibrium properties of quantum matter are theoretically described with great success. Yet, in recent years pioneering experiments have created quantum states beyond this equilibrium paradigm. Understanding properties of such nonequilibrium quantum states on a general level provides a significant challenge. Jurcevic at el. have now experimentally observed for the first time a phenomenon - a dynamical quantum phase transition - which promises to provide a general framework to identify and predict such general principles of quantum dynamics.

See also the Physics Viewpoint: Quantum Phase Transitions Go Dynamical
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Awards and Honors

External Scientific Member Prof. Dr. Peter Grassberger receives EPS Statistical and Nonlinear Physics Prize 2017

for his seminal contributions to nonlinear physics
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Awards and Honors

Edgar Roldan receives EPS-SNPD Early Career prize 2017

for his outstanding contribution in the area of statistical physics and stochastic thermodynamics.
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Publication Highlights

Pump-Power-Driven Mode Switching in a Microcavity Device and Its Relation to Bose-Einstein Condensation

H.A.M. Leymann et al., Phys. Rev. X 7, 021045 (2017)

We investigate the switching of the coherent emission mode of a bimodal microcavity device, occurring when the pump power is varied. We compare experimental data to theoretical results and identify the underlying mechanism based on the competition between the effective gain, on the one hand, and the intermode kinetics, on the other. When the pumping is ramped up, above a threshold, the mode with the largest effective gain starts to emit coherent light, corresponding to lasing. In contrast, in the limit of strong pumping, it is the intermode kinetics that determines which mode acquires a large occupation and shows coherent emission. We point out that this latter mechanism is akin to the equilibrium Bose-Einstein condensation of massive bosons. Thus, the mode switching in our microcavity device can be viewed as a minimal instance of Bose-Einstein condensation of photons. Moreover, we show that the switching from one cavity mode to the other always occurs via an intermediate phase where both modes are emitting coherent light and that it is associated with both superthermal intensity fluctuations and strong anticorrelations between both modes.
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Publication Highlights

Neutron scattering in the proximate quantum spin liquid a-RuCl3

Arnab Banerjee et al. Science 356, 1055 (2017)

The Kitaev quantum spin liquid (KQSL) is an exotic emergent state of matter exhibiting Majorana fermion and gauge flux excitations. The magnetic insulator ?-RuCl3 is thought to realize a proximate KQSL. We used neutron scattering on single crystals of ?-RuCl3 to reconstruct dynamical correlations in energy-momentum space. We discovered highly unusual signals, including a column of scattering over a large energy interval around the Brillouin zone center, which is very stable with temperature. This finding is consistent with scattering from the Majorana excitations of a KQSL. Other, more delicate experimental features can be transparently associated with perturbations to an ideal model. Our results encourage further study of this prototypical material and may open a window into investigating emergent magnetic Majorana fermions in correlated materials.

See also: A. Banerjee et al. Nature Materials, 15, 733 (2016).
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Publication Highlights

Equilibration and Order in Quantum Floquet Matter

R. Moessner and S. L. Sondhi, Nature Physics 13, 424 (2017)

Equilibrium thermodynamics is characterized by two fundamental ideas: thermalization—that systems approach a late time thermal state; and phase structure—that thermal states exhibit singular changes as various parameters characterizing the system are changed. We summarize recent progress that has established generalizations of these ideas to periodically driven, or Floquet, closed quantum systems. This has resulted in the discovery of entirely new phases which exist only out of equilibrium, such as the ?-spin glass/Floquet time crystal.

This is a progress article. For related original work see: Phase Structure of Driven Quantum Systems, Khemani et al. Phys. Rev. Lett. 116, 250401 (2016).
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