Welcome! We are carrying out research in the field of quantum optics and quantum many-body systems using ultracold atomic and molecular quantum gases at the Max-Planck Institute for Quantum Optics and the Ludwig-Maximilians University. Furthermore, our group is part of the Munich Quantum Center.
If you are interested in joining our team click here!
Quantum phase transitions are characterized by a dramatic change of the ground-state behavior; famous examples include the appearance of magnetic order or superconductivity as a function of doping in cuprates.
In this work, we explore how a system dynamically crosses such a transition and investigate in detail how coherence emerges when an initially incoherent Mott insulating system enters the superfluid regime.
One of the leading experts in theoretical condensed matter physics, Professor Eugene Demler from Harvard University (Cambridge, USA), has joined the LMU and MPQ as a winner of a Humboldt Research Award. This Award is granted by the Alexander von Humboldt Foundation to out-standing foreign academics in order to promote cooperation with excellent German researchers. Prof. Demler was nominated by Prof. Immanuel Bloch and Prof. Wilhelm Zwerger (TU München) who will host him during his stay in Germany. Having started his visit on January 20th Demler will work in Munich until March 20th, and then again from May to July next year.
Chern numbers are topological invariants characterizing Bloch bands. A striking manifestation of non-zero Chern numbers is the quantization of the Hall conductivity revealed by the quantum Hall effect. Here, we report on the first non-electronic Chern-number measurement with ultracold bosonic atoms that were loaded into an optical lattice potential subjected to artificial gauge fields. By applying a linear force to the atoms they experience a transverse motion proportional to the Chern number of the occupied band. By analyzing the in-situ evolution of the cloud we determined an experimental value of the Chern number νexp=0.99(5) in agreement with theory.
Nature Physics 11, 162-166 (2015), AOP 3171 (2014)
See also: Commentary by Wolfgang Ketterle
The geometric structure of a single-particle energy band in a solid is fundamental for a wide range of many-body phenomena and is uniquely characterized by the distribution of Berry curvature over the Brillouin zone. We have demonstrated a matter-wave interferometer that precisely measures Berry curvature in an graphene-like optical honeycomb lattice and could demonstrate the highly singular nature of the Dirac point.
See also: Science perspective by A. Lamacroft
Check out our article for the general reader in 'Spektrum der Wissenschaft' (the german issue of Scientific American) in the SdW, Nov. 2014 issue on 'Simulated Quantum Worlds'.
We studied far-from equilibrium spin transport in Heisenberg quantum magnets. For 1D systems we explain the observed diffusion like transport microscopically by the spectral properties of the Hamiltonian. In contrast, 2D Heisenberg magnets show anomalous superdiffusion.
Using the two stable electronic states of ytterbium, we were able to observe an orbital spin-exchange interaction - the building block of orbital quantum magnetism - in a SU(N)-symmetric fermionic quantum gas. Spin-exchanging interactions and SU(N) spin symmetry in ytterbium were so far only predicted theoretically, and their experimental observation paves the way for the experimental study of previously inaccessible quantum many-body phenomena.
Nature Physics AOP 3061 (2014)
Prof. Cheng Chin, winner of a Humboldt Research Award, will join our group for his research sabbatical in the beginning of August 2014. Prof. Chin studies quantum many-body phenomena based on ultracold atoms and molecules at the University of Chicago, including phenomena from different branches of physics such as nuclear, condensed matter, gravitational and astro-physics. During his stay in Munich he will work in close cooperation with our group at LMU and MPQ, as well as the group of Prof. Wilhelm Zwerger at TUM.
We implemented a ladder system with uniform magnetic field using ultracold atoms in optical lattices. By measuring the currents along the legs of the ladder we were able to observe a transition from a Meissner-like phase to a vortex phase.
By using a combination of Ramsey interferometry and Bloch oscillations we implement a protocol to extract the geometric phase of a one-dimensional dimerized optical lattice modelling polyacetylene. This one-dimensional Berry phase, also known as Zak phase, can be viewed as an invariant characterizing the topological properties of the energy bands.
We implemented large uniform effective magnetic fields with ultracold atoms using laser-assisted tunneling in a tilted optical lattice. We also show that for two atomic spin states with opposite magnetic moments, our system naturally realizes the time-reversal-symmetric Hamiltonian underlying the quantum spin Hall effect. Phys. Rev. Lett. 111, 185301 (2013)
Using our quantum gas microscope we succeeded to observe magnon bound states in one-dimensional quantum magnets. These two-body bound states have been predicted to exist in Heisenberg chains by Hans Bethe 80 years ago. Using a novel microscopic preparation and detection method we identify the states by their characteristic correlations and, furthermore, we observe their dynamics. Nature 502, 76–79 (2013), Press Release MPQ (english, deutsch).
See also: News and views by Sougato Bose
Manuel Endres receives the PhD prize of the "Münchner Universitätsgesellschaft" for his thesis "Probing correlated quantum many-body systems at the single-particle level".
We observed coherent motion of a single spin down atom embedded in an environment of spin up atoms. Our measurements revealed coherent superexchange dynamics over large distances in the Mott insulating regime. In the superfluid regime we observed polaronic physics which lead to a reduced spreading speed due to the strong impurity-bath interactions. Nature Physics 9, 235-241 (2013), Press Release MPQ (english, deutsch).
See also: News and views by Patrick Windpassinger
We could for the first time observe a negative absolute temperature for mobile particles. By using an intermediate bosonic Mott insulator together with a Feshbach resonance in bosonic Potassium we were able to create a stable attractive Bose gas at negative absolute temperature.
Science 339, 52 (2013).
Prof. Nigel Cooper, winner of a Humboldt Research Award, has joined our group in January 2013 as a guest scientist for three months. Nigel Cooper is an internationally renowned Professor of Theoretical Physics at the University of Cambridge where he leads a group working on Theory of Condensed Matter, and he is Fellow of Pembroke College. During his stay in Munich he will work in the field of artificial gauge fields and topological phases with our group at MPQ and LMU, as well as the group of Prof. Wilhelm Zwerger at TUM.
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Group seminar LMU: Felix Binder
Tuesday, 31.02.2015 10:00 a.m. (s.t.) in H107, Fakultät für Physik, LMU
Felix Binder, Oxford
Group seminar LMU: Prospects for controlling Fermi-Hubbard physics on the single-atom level
Tuesday, 17.02.2014 10:00 a.m. (s.t.) in H107, Fakultät für Physik, LMU
Thomas Lompe, MIT
Max-Planck-Institut für Quantenoptik
85748 Garching, Germany
Phone: +49 (0)89 32905 - 138
Fax: +49 (0)89 32905 - 313
Quantum Optics Chair/
Fakultät für Physik
80799 Munich, Germany
Phone: +49 (0)89 2180 - 6131
Fax: +49 (0)89 2180 - 63850