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TT: Fachverband Tiefe Temperaturen

TT 11: Poster Session: Matter at Low Temperature

TT 11.19: Poster

Monday, March 14, 2011, 14:00–18:00, P4

Relaxation phenomena in ultracold atomic systems after quenching the external potential — •Akos Rapp, Stephan Mandt, and Achim Rosch — Institute f. Theoretical Physics, Uni Cologne, Cologne, Germany

In contrast to the subjects of traditional solid state physics, ultracold atoms offer ways to realize and study states of matter without the influence of background degrees of freedom, impurities, etc. Furthermore, one can change the shapes and strengths of external potentials relatively easy, to investigate dynamics out of equilibrium. We study how a cloud of ultracold atoms in equilibrium in a harmonic trap evolves after the potential is changed suddenly. Without an optical lattice, the physics is usually relatively simple. However, in a deep optical lattice the kinetic energy is bounded, leading to unexpected relaxation phenomena. Even by simply turning the confining potential off, the system evolves through a nontrivial interplay of diffusive and ballistic motion of the atoms [arXiv:1005.3545], while reversing the sign of the harmonic potential allows equilibration to negative absolute temperatures, T<0 [PRL 105, 220405 (2010)]. We discuss direct experimental consequences of different external potential quenches and the common aspects of these out of equilibrium processes.