From a non-thermal fixed point to thermal equilibrium with one-dimensional Bose gases

Abstract

On the macroscopic level novel, and even universal, phenomena can emerge. The underlying loss of information makes these phenomena insensitive to microscopic details and thus renders them interesting for quantum simulations. I will present experimental studies with 87Rb spinor Bose-Einstein condensates obtained in the Oberthaler group in Heidelberg. Employing quantum quenches, we bring the system out of equilibrium and observe transient universal phenomena associated with the emergence of a non-thermal fixed point [1] and a suppression of the four-vertex at low momenta in the highly occupied regime [2]. We follow the system’s dynamics beyond the non-thermal fixed point and observe its approach to thermal equilibrium. We characterize the underlying quasi-particle excitations by probing the dispersion relations. We find two Goldstone modes which are associated with the emergence of long-range coherence in the density and spin degree of freedom [3].