Highlights

Am 6. Februar 2017, 16.30 Uhr wird am Max-Planck-Institut für Physik komplexer Systeme (MPI-PKS) erstmalig der „Physik-Preis Dresden“ von der TU Dresden und dem MPI-PKS verliehen. Der diesjährige Preisträger ist Professor Daniel P. Arovas von der University of California, San Diego. Zu diesem Anlass hält Professor Arovas einen Preiskolloquiumsvortrag zum Thema "The Amplitude Mode in Condensed Matter: Higgs Hunting on a Budget". Professor Arovas hat bahnbrechende Beiträge zur Festkörperphysik geleistet, insbesondere zur Theorie des Magnetismus und der Physik niedrigdimensionaler Systeme. Nach dem Physikstudium an der Universität Princeton hat Professor Arovas in Santa Barbara an der University of California promoviert, woraufhin er in Chicago Postdoc war. Er war außerdem Visiting Professor in Princeton, Stanford und Haifa. Der Physik-Preis Dresden, welcher von Professor Peter Fulde, dem Gründungsdirektor des MPI-PKS gestiftet wurde, wird dieses Jahr erstmals vergeben. Der/die Preisträger/in wird von einer gemeinsamen Kommission der TU Dresden und des MPI-PKS bestimmt, wobei neben dem zentralen Kriterium der wissenschaftlichen Exzellenz wichtig ist, dass seine/ihre Arbeiten für die Zusammenarbeit zwischen diesen beiden Institutionen von Bedeutung sind. In diesem Sinne verstärkt dieser Preis deren langjährige Kooperation, welche in letzter Zeit auch institutionell erweitert wurde, z.B. mit der Gründung des Dresden concept e.V. im Rahmen der Exzellenzinitiative. Professor Arovas hat bestehende Kollaborationen mit Physikern von der TU Dresden, und sein Forschungsfeld hat großen Überlapp mit dem Sonderforschungsbereich „Korrelierter Magnetismus: Von Frustration zu Topologie", an dem Physiker und Chemiker aus der TU sowie mehreren außeruniversitären Forschungsinstituten in Dresden beteiligt sind.

Christine Muschik, Markus Heyl, et al., arXiv:1612.08653

Lattice gauge theories describe fundamental phenomena in nature, but calculating their real-time dynamics on classical computers appears to be notoriously difficult. Digital quantum simulation has been proposed as a general strategy to solve such computationally hard problems on a programmable quantum device instead of using conventional computers. Recently, an experiment has demonstrated for the first time a digital quantum simulation of a lattice gauge theory on a small-scale quantum computer made of trapped ions. This work has been selected by the magazine Physics World as one of the top ten breakthroughs in physics in 2016. Now, a detailed theoretical analysis of the experimentally used scheme has been published which studies in detail the scheme's performance, robustness against various error sources, and scalability.

See also coverage in Physics World and the experimental work .

V. Zaburdaev, I. Fouxon, S. Denisov, and E. Barkai, Phys. Rev. Lett. 117, 270601

It is recognized now that a variety of real-life phenomena ranging from diffusion of cold atoms to the motion of humans exhibit dispersal faster than normal diffusion. Lévy walks is a model that excelled in describing such superdiffusive behaviors albeit in one dimension. Here we show that, in contrast to standard random walks, the microscopic geometry of planar superdiffusive Lévy walks is imprinted in the asymptotic distribution of the walkers. The geometry of the underlying walk can be inferred from trajectories of the walkers by calculating the analogue of the Pearson coefficient.

We are glad to announce the arrival of Dr. Steffen Rulands, who heads the research group 'Statistical Physics of Living Systems' since 1 January 2017. The group will investigate mechanisms of collective cellular decision making in tissue development, maintenance and disease.

Vasily Zaburdaev (MPI-PKS), Simon Alberti (MPI-CBG), Teymuras Kurzchalia (MPI-CBG) and Jochen Guck (BIOTEC, TU Dresden) receive a 1.3 million Euro grant from the Volkswagen Foundation (VolkswagenStiftung). The joint project focuses on the underlying biological, chemical, and physical mechanisms of cell dormancy.

Gary S. Klindt, Christian Ruloff, Christian Wagner, and Benjamin M. Friedrich, Phys. Rev. Lett. 117, 258101 (2016)

Cilia and flagella exhibit regular bending waves that perform mechanical work on the surrounding fluid, to propel cellular swimmers and pump fluids inside organisms. Here, we quantify a force-velocity relationship of the beating flagellum, by exposing flagellated Chlamydomonas cells to controlled microfluidic flows. A simple theory of flagellar limit-cycle oscillations, calibrated by measurements in the absence of flow, reproduces this relationship quantitatively. We derive a link between the energy efficiency of the flagellar beat and its ability to synchronize to oscillatory flows.

Frank Jülicher erhält den wichtigsten deutschen Forschungsförderpreis für seine herausragenden Beiträge zur theoretischen Biophysik. Der Gottfried Wilhelm Leibniz Preis wird von der Deutschen Forschungsgemeinschaft verliehen und geht in diesem Jahr an 3 Wissenschaftlerinnen und 7 Wissenschaftler. Der Leibniz-Preis ist mit 2.5 Millionen Euro Forschungsgeldern dotiert.


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J. Nasu, J. Knolle, D. L. Kovrizhin, Y. Motome and R. Moessner Nature Physics (2016)

Conventionally ordered magnets possess bosonic elementary excitations, called magnons. By contrast, no magnetic insulators in more than one dimension are known whose excitations are not bosons but fermions. Theoretically, some quantum spin liquids (QSLs)—new topological phases that can occur when quantum fluctuations preclude an ordered state—are known to exhibit Majorana fermions as quasiparticles arising from fractionalization of spins. Alas, despite much searching, their experimental observation remains elusive. Here, we show that fermionic excitations are remarkably directly evident in experimental Raman scattering data across a broad energy and temperature range in the two-dimensional material α-RuCl3. This shows the importance of magnetic materials as hosts of Majorana fermions. In turn, this first systematic evaluation of the dynamics of a QSL at finite temperature emphasizes the role of excited states for detecting such exotic properties associated with otherwise hard-to-identify topological QSLs.

Vedika Khemani, Achilleas Lazarides, Roderich Moessner, and S.L. Sondhi Phys. Rev. Lett. 116, 250401 (2016)

Clean and interacting periodically driven systems are believed to exhibit a single, trivial “infinite-temperature” Floquet-ergodic phase. In contrast, here we show that their disordered Floquet many-body localized counterparts can exhibit distinct ordered phases delineated by sharp transitions. Some of these are analogs of equilibrium states with broken symmetries and topological order, while others—genuinely new to the Floquet problem—are characterized by order and nontrivial periodic dynamics. We illustrate these ideas in driven spin chains with Ising symmetry.

Martin Gerlach, Francesc Font-Clos, and Eduardo G. Altmann, Phys. Rev. X 6, 021009 (2016)

Quantifying the similarity between symbolic sequences is a traditional problem in information theory which requires comparing the frequencies of symbols in different sequences. In numerous modern applications, ranging from DNA over music to texts, the distribution of symbol frequencies is characterized by heavy-tailed distributions (e.g., Zipf’s law). The large number of low-frequency symbols in these distributions poses major difficulties to the estimation of the similarity between sequences; e.g., they hinder an accurate finite-size estimation of entropies. Here, we show analytically how the systematic (bias) and statistical (fluctuations) errors in these estimations depend on the sample size N and on the exponent γ of the heavy-tailed distribution. Our results are valid for the Shannon entropy (α=1), its corresponding similarity measures (e.g., the Jensen-Shanon divergence), and also for measures based on the generalized entropy of order α. For small α’s, including α=1, the errors decay slower than the 1/N decay observed in short-tailed distributions. For α larger than a critical value α*=1+1/γ <= 2, the 1/N decay is recovered. We show the practical significance of our results by quantifying the evolution of the English language over the last two centuries using a complete α spectrum of measures. We find that frequent words change more slowly than less frequent words and that α=2 provides the most robust measure to quantify language change.

See also coverage in Physics Today and Physics.