Photo-induced nonequilibrium states in Mott insulators

TL;DR

This paper reviews the mechanisms and properties of photo-induced nonequilibrium states in Mott insulators, highlighting recent theoretical and experimental advances in understanding transient phases and metastable states induced by light.

Contribution

It provides a comprehensive overview of the current theoretical and experimental understanding of photo-induced states in Mott insulators, linking concepts to observed phenomena.

Findings

Identification of key mechanisms controlling charge carrier dynamics

Observation of nonthermal electronic orders in photo-excited Mott systems

Analysis of various driving fields inducing nonequilibrium states

Abstract

The study of nonequilibrium phenomena in interacting lattice systems can provide new perspectives on correlation effects, and information on metastable states of matter. Mott insulators are a promising class of systems for nonequilibrium studies, since they exhibit exotic phenomena and complex phase diagrams upon doping, and because a large Mott gap provides protection against fast thermalization and heating after photo-excitations. We can thus expect the emergence of interesting transient states and photo-induced phases in Mott systems. This review presents the current understanding of the mechanisms which control the time evolution of photo-doped charge carriers and the properties of photo-induced metastable states. We focus on recent theoretical progress, identify the relevant underlying concepts, and link them to experimental observations. The review starts with a general discussion of field-induced nonequilibrium setups and an overview of key experiments which revealed characteristic properties of photo-excited Mott states, proceeds with a compact overview of the theoretical tools which have been developed to investigate these strongly correlated nonequilibrium states, and then analyzes Mott insulators driven out of equilibrium by static electric fields, periodic fields, and short laser pulses. We also discuss the appearance of nonthermal electronic orders in photo-excited Mott systems, including nonthermal spin and orbital orders, $\eta$ pairing states, and novel types of excitonic orders.