Highlights

Prof. Dr. Frank Jülicher wurde zum ordentlichen Mitglied der Mathematisch-naturwissenschaftlichen Klasse der Akademie der Wissenschaften und der Literatur, Mainz gewählt.

We provide a complete and exact theoretical study of the dynamical structure factor of a two-dimensional quantum spin liquid in gapless and gapped phases, as realized in Kitaev’s honeycomb model. We show that there are direct signatures—qualitative and quantitative—of the Majorana fermions and gauge fluxes emerging in this model. These include counterintuitive manifestations of quantum number fractionalization, such as a neutron scattering response with a gap even in the presence of gapless excitations, and a sharp component despite the fractionalization of electron spin. Our analysis identifies new varieties of the venerable x-ray edge problem and explores connections to the physics of quantum quenches. J. Knolle, D. L. Kovrizhin, J.T. Chalker, and R. Moessner Phys. Rev. Lett. 112, 207203 (2014)

Collective behavior in many-body systems is the origin of many fascinating phenomena in nature, ranging from the formation of clouds to magnetic properties of solids. We report on the observation of collective spin dynamics in an ultracold Fermi sea with large spin. As a key result, we observed long-lived and large-amplitude coherent spin oscillations driven by local spin interactions. At ultralow temperatures, Pauli blocking stabilizes the collective behavior, and the Fermi sea behaves as a single entity in spin space. With increasing temperature, we observed a stronger damping associated with particle-hole excitations. Unexpectedly, we found a high-density regime where excited spin configurations are collisionally stabilized. Our results reveal the intriguing interplay between microscopic processes either stimulating or suppressing collective effects in a fermionic many-body system. J.S. Krauser, U. Ebling, N. Fläschner, J. Heinze, K. Sengstock, M. Lewenstein, A. Eckardt, and C. Becker, Science 343, 157 (2014)

Dr. Michael Hiller, Gurppenleiter am Max-Planck-Institut für Physik komplexer Systeme und am Max-Planck-Institut für molekulare Zellbiologie und Genetik in Dresden, erhält den German Life Science Awrad. Der Bioinformatiker vergleicht das Erbgut von Menschen, Affen und anderen Tieren, um die Unterschiede zwischen den Arten mit den Abweichungen in ihren Genen zu korrelieren. Seine Ergebnisse könnten auch der Medizin nützen.

Der Wissenschaftler überzeugte die unabhängige Fachjury mit seinem Beitrag über das Zusammenspiel von mechanischen und biochemischen Signalen für den biologischen Prozess der Zellpolarisation.

Seit 1978 zeichnet die Max-Planck-Gesellschaft jedes Jahr junge Wissenschaftlerinnen und Wissenschaftler für herausragende wissenschaftliche Leistungen, die sie in der Regel im Zusammenhang mit ihrer Doktorarbeit erbracht haben, mit der Otto-Hahn-Medaille aus. Diese ist mit einem Anerkennungsbetrag von 7500 Euro verbunden.

The eukaryotic flagellum is a best-seller of nature: These slender cell appendages propel sperm and many other microswimmers, including disease-causing protists. In mammalian airways or the oviduct, collections of flagella beat in synchrony to pump fluids efficiently. Flagellar synchronization was proposed to rely on mechanical feedback by hydrodynamic forces, but the details are not well understood. Here, we used theory and experiment to elucidate a mechanism of synchronization in the model organism Chlamydomonas, a green algal cell that swims with two flagella like a breaststroke swimmer. Our analysis shows how synchronization arises by a coupling of swimming and flagellar beating and characterizes an exemplary force–velocity relationship of the flagellar beat. Veikko F. Geyer, Frank Jülicher, Jonathon Howard, and Benjamin M. Friedrich PNAS 110 (45), 18058 (2013)

The new research group is headed by Dr. Jens Bardarson and studies quantum matter, condensed matter which properties are dominated by quantum effect, with focus ranging from fundamental theory to direct comparison and collaboration with experimental groups, in particular in Dresden.

The junior research group headed by Dr. Jan Brugués is affiliated with both our institute and the MPI of Molecular Cell Biology and Genetics. It is focused on understanding how the large-scale patterns and behaviors of biological structures emerge from the collective behaviors of molecules.

Magnetism plays a key role in modern science and technology, but still many open questions arise from the interplay of magnetic many-body interactions. Deeper insight into complex magnetic behaviour and the nature of magnetic phase transitions can be obtained from, for example, model systems of coupled XY and Ising spins. Here, we report on the experimental realization of such a coupled system with ultracold atoms in triangular optical lattices. This is accomplished by imposing an artificial gauge field on the neutral atoms, which acts on them as a magnetic field does on charged particles. As a result, the atoms show persistent circular currents, the direction of which provides an Ising variable. On this, the tunable staggered gauge field, generated by a periodic driving of the lattice, acts as a longitudinal field. Further, the superfluid ground state presents strong analogies with the paradigm example of the fully frustrated XY model on a triangular lattice. J. Struck, M. Weinberg, C. Ölschläger, P. Windpassinger, J. Simonet, K. Sengstock, R. Höppner, P. Hauke, A. Eckardt, M. Lewenstein & L. Mathey Nature Physics 9, 738–743 (2013)