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A: Fachverband Atomphysik

A 16: Ultra-cold atoms, ions, and BEC (joint session A/Q)

A 16.1: Poster

Mittwoch, 22. September 2021, 16:30–18:30, P

Observation of a universal entropy behaviour for impurities in an ultracold bath — •Silvia Hiebel, Jens Nettersheim, Julian Feß, Sabrina Burgardt, Daniel Adam, and Artur Widera — Physics Department and State Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Str. 46, 67663 Kaiserslautern, Germany

Nonequilibrium systems usually thermalize by gradually increasing their entropy to a new equilibrium state. For systems very far from equilibrium, however, another pathway has been predicted¹, where rapidly a state of high entropy, close to the maximal entropy possible for this system, is reached. The dynamic following this so-called prethermal memory loss is predicted to be universal.
We experimentally realize such nonequilibrium dynamics in the spin manifold of single Cs impurities undergoing spin-exchange collisions with a large Rb bath. The maximum entropy of the quantum spin distribution is reached after a few spin-exchange collisions starting from a spin-polarized, low entropy state. Rescaling the following spin-distribution dynamics when maximum entropy is reached, we find the trace of each spin state identical, independent of the initially prepared spin state. We analyse and describe these mechanisms in terms of the drift and diffusion of the quantum spin distribution. Our work thus illustrates the existence of universal, prethermal dynamics in open quantum systems far from equilibrium.
¹Ling-Na Wu and André Eckardt, PRB 101, 220302 (2020)