Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 37: Cold Atomic Gases

TT 37.3: Talk

Tuesday, April 1, 2014, 10:15–10:30, HSZ 304

Relaxation towards negative temperatures in bosonic systems: generalized Gibbs ensembles and beyond integrability — Stephan Mandt¹, Adrian E. Feiguin², and •Salvatore R. Manmana³ — ¹Princeton Center for Complex Materials and Department of Physics, Princeton University, NJ 08544, USA. — ²Department of Physics, Northeastern University, Boston, MA 02115, USA. — ³Institute for Theoretical Physics, University of Göttingen, D-37077 Göttingen, Germany.

Motivated by the recent experimental observation of negative absolute temperature states in systems of ultracold atomic gases on optical lattices [Braun et al., Science 339, 52-55 (2013)], we investigate theoretically the formation of these states. More specifically, we consider the relaxation after a sudden inversion of the external parabolic confining potential in the one-dimensional inhomogeneous Bose-Hubbard model. First, we focus on the integrable hard-core boson limit which allows us to treat large systems and arbitrarily long times, providing convincing numerical evidence for relaxation to a generalized Gibbs ensemble at negative temperatures T < 0, being defined by us in this context. Second, going beyond one dimension, we demonstrate that the emergence of negative temperature states can be understood in a dual way in terms of positive temperatures, which relies on a dynamic symmetry of the Hubbard model. We complement the study by exact diagonalization simulations at finite values of the on-site interaction.