## IPB COLLOQUIUM: Walter Hofstetter, 11 October 2016

You are cordially invited to the IPB COLLOQUIUM which will be held on Tuesday, 11 October 2016 at 12:00 in “Dr. Dragan Popović” library reading room of the Institute of Physics Belgrade. The talk entitled

INTERACTING TOPOLOGICAL STATES AND MAGNETISM IN ULTRACOLD LATTICE GASES

will be given by Prof. Dr. Walter Hofstetter (University of Frankfurt, Germany).

Abstract of the talk:

The last years have witnessed dramatic progress in experimental control and theoretical modeling of quantum simulations based on ultracold atoms. Major recent developments are synthetic gauge fields for neutral atoms, allowing the simulation of topologically nontrivial phases of matter with strong interactions, and predictions for exotic types of spin order beyond those occuring in electronic solid-state materials. We will present two examples:

We consider a spinful and time-reversal invariant version of the Hofstadter-Harper problem, which has been realized in ultracold atoms. In these experiments, an additional staggered potential and spin-orbit coupling are available. Without interactions, the system exhibits various phases such as topological and normal insulator, metal and semi-metal phases with two or even more Dirac cones. Using real-space dynamical mean-field theory (DMFT), we investigate the stability of the Quantum Spin Hall state in the presence of strong interactions. To test the bulk-boundary correspondence between edge mode parity and bulk Chern index of the interacting system, we calculate an effective topological Hamiltonian based on the local self-energy of DMFT.

We furthermore investigate strongly correlated spin-1 ultracold bosons with antiferromagnetic interactions in a cubic optical lattice, based on bosonic DMFT. A rich phase diagram of the system is mapped out both at zero and finite temperature, and the existence of a spin-singlet condensate is established. At finite temperature, we find that the superfluid can be heated into a Mott insulator, analogous to the Pomeranchuk effect in He_3.