Ultra-fast photo-carrier relaxation in Mott insulators with short-range spin correlations

TL;DR

This study reveals that in two-dimensional Mott insulators, the relaxation rate of photo-doped electrons is strongly influenced by short-range spin correlations, with relaxation times increasing with temperature and excitation density, using a nonequilibrium DCA approach.

Contribution

The paper introduces a nonequilibrium dynamical cluster approximation to analyze photo-carrier relaxation, highlighting the role of short-range spin correlations in Mott insulators.

Findings

Relaxation rate scales with nearest-neighbor spin correlations.

Higher temperature and excitation density increase relaxation times.

Finite doping introduces additional scattering channels, speeding up relaxation.

Abstract

We compute the time-resolved photoemission spectrum after photo-doping in a two-dimensional Mott-Hubbard insulator. We find that the relaxation rate of high-energy photo-doped electrons in the paramagnetic phase scales with the strength of the nearest-neighbor spin correlations, which implies a pronounced increase of the relaxation times with temperature and excitation density. Finite doping, in contrast, opens additional scattering channels and leads to a faster relaxation. To obtain our results we have implemented a nonequilibrium version of the dynamical cluster approximation (DCA), which, in contrast to single-site dynamical mean-field theory, captures the effect of short-range correlations.