Tuning the relaxation dynamics of ultracold atoms with an optical cavity

TL;DR

This paper explores the complex out-of-equilibrium behavior of ultracold atoms in optical lattices coupled to optical cavities, revealing diverse relaxation dynamics and steady states influenced by cavity regimes and interactions.

Contribution

It derives a comprehensive quantum master equation for weak atom-light coupling applicable in different cavity regimes, uncovering novel diffusion behaviors and cavity cooling mechanisms.

Findings

Steady state is always infinite temperature in bad cavity regime.

Anomalous diffusion occurs due to dissipation and interactions for small hopping.

Optical pumping enables cavity cooling in the good cavity regime.

Abstract

We investigate the out-of-equilibrium dynamics of ultracold atoms trapped in an optical lattice and loaded into an optical resonator that is driven transversely. We derive an effective quantum master equation for weak atom-light coupling that can be brought into Lindblad form both in the bad and good cavity limits. In the so-called bad cavity regime, we find that the steady state is always that of infinite temperature, but that the relaxation dynamics can be highly non-trivial. For small hopping, the interplay between dissipation and strong interactions generally leads to anomalous diffusion in the space of atomic configurations. However, for a fine-tuned ratio of cavity-mediated and on-site interactions, we discover a limit featuring normal diffusion. In contrast, for large hopping and vanishing on-site interactions, the system can be described by a linear rate equation leading to an exponential approach of the infinite-temperature steady state. Finally, in the good cavity regime, we show that for vanishing on-site interactions, the system allows for optical pumping between momentum mode pairs enabling cavity cooling.