Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 69: Other Low Temperature Topics: Cold Atomic Gases

TT 69.6: Talk

Wednesday, March 18, 2015, 16:15–16:30, A 053

Relaxation of oscillations in a mass-imbalanced mixture of trapped ultracold Fermi gases — •Robert Bamler and Achim Rosch — University of Cologne, Germany

We present theoretical results on the center-of-mass oscillations of a mixture of two ultracold Fermi gases trapped in a harmonic potential. We investigate the dependency of the relaxation time on the mass difference and on the strength of the scattering between the two fermion species.

Ultracold atomic gases allow for the study of many-particle systems under highly controllable conditions. As interactions with the environment can be reduced to negligible amounts, these systems can be used to study the dynamics far from equilibrium and, in particular, the relaxation towards equilibrium due to collisions between the system's constituents.

We consider a mixture of two species of fermionic atoms in a harmonic trap. If both atom species have the same mass, then the center-of-mass oscillation of the atomic cloud around its equilibrium position is undamped even in the presence of interactions between the atoms. Moreover, Kohn's theorem states that the oscillation frequency is independent of the interaction strength. The situation changes if the two atomic species have slightly different masses. In this case, inter-species collisions lead to finite relaxation times for the two oscillatory modes and, with growing interaction strength, a merging of the two oscillatory modes. We study this transition quantitatively by investigating the memory matrix of the macroscopic coordinates.