Diehl, Sebastian

Date: Friday May 8, 2015
Time: 14:00
Place: ETH Zurich, Hönggerberg, HPF G 6
Host: Atac Imamoglu

Universal phenomena in driven open quantum systems

Sebastian Diehl
TU Dresden, Germany

Quantum optics and many-body physics increasingly merge together in ultracold atomic gases and certain classes of solid state systems. This gives rise to new non-equilibrium scenarios in stationary state, where coherent and dissipative dynamics appear on an equal footing.

Here we report on dynamical critical phenomena of non-equilibrium Bose condensation transitions in many-body ensembles subject to particle loss and pumping. The microscopic drive conditions are witnessed even on the largest scales via a new, independent universal critical exponent characterizing decoherence. This defines a non-equlibrium analog of classical dynamical criticality. We then discuss a non-equilibrium analog of quantum dynamical criticality, with a possible realization in microcavity arrays. The corresponding interacting critical fixed point retains coherence even at the largest distances. Furthermore, we address ordering phenomena in two dimensions. We show that driven Bose systems cannot exhibit algebraic quasi-long range order, unless being strongly anisotropic. While the correlations thus generically do not show signatures of order, we demonstrate that the superfluid response, surprisingly, is finite. These results hint at a genuine phase transition visible in the responses but not the correlations, without counterpart in equilibrium.