Thermalization of a pump-excited Mott insulator

TL;DR

This paper investigates how a Mott insulator relaxes after laser excitation, revealing different thermalization behaviors depending on interaction strength, and showing that simple equilibrium descriptions fail in strongly excited states.

Contribution

It applies nonequilibrium dynamical mean-field theory with a strong-coupling impurity solver to analyze the thermalization process in pump-excited Mott insulators, highlighting different regimes and breakdown of quasi-equilibrium.

Findings

Thermalization time varies with interaction strength.

Strong interactions lead to exponentially slow thermalization.

Rapid thermalization occurs when interactions are comparable to bandwidth.

Abstract

We use nonequilibrium dynamical mean-field theory in combination with a recently implemented strong-coupling impurity solver to investigate the relaxation of a Mott insulator after a laser excitation with frequency comparable to the Hubbard gap. The time evolution of the double occupancy exhibits a crossover from a strongly damped transient at short times towards an exponential thermalization at long times. In the limit of strong interactions, the thermalization time is consistent with the exponentially small decay rate for artificially created doublons, which was measured in ultracold atomic gases. When the interaction is comparable to the bandwidth, on the other hand, the double occupancy thermalizes within a few times the inverse bandwidth along a rapid thermalization path in which the exponential tail is absent. Similar behavior can be observed in time-resolved photoemission spectroscopy. Our results show that a simple quasi-equilibrium description of the electronic state breaks down for pump-excited Mott insulators characterized by strong interactions.