Coupled charge and spin dynamics in a photo-excited Mott insulator

TL;DR

This paper investigates the coupled charge and spin relaxation dynamics in a photo-excited Mott insulator using nonequilibrium EDMFT, revealing how different excitation regimes influence relaxation processes and the potential for experimental detection of string states.

Contribution

It introduces a nonequilibrium EDMFT approach to study charge-spin dynamics in the $t$-$J$ model, highlighting the role of string states and excitation strength in relaxation behavior.

Findings

String states cause nontrivial relaxation scaling.

Weak excitation leads to oscillatory charge-spin dynamics.

Strong excitation suppresses spin correlations and alters relaxation.

Abstract

Using a nonequilibrium implementation of the extended dynamical mean field theory (EDMFT) we simulate the relaxation after photo excitation in a strongly correlated electron system with antiferromagnetic spin interactions. We consider the $t$-$J$ model and focus on the interplay between the charge- and spin-dynamics in different excitation and doping regimes. The appearance of string states after a weak photo excitation manifests itself in a nontrivial scaling of the relaxation time with the exchange coupling and leads to a correlated oscillatory evolution of the kinetic energy and spin-spin correlation function. A strong excitation of the system, on the other hand, suppresses the spin correlations and results in a relaxation that is controlled by hole scattering. We discuss the possibility of detecting string states in optical and cold atom experiments.