Photoinduced insulator-metal transition and nonlinear optical response of correlated electrons -- a DMFT analysis

TL;DR

This study uses nonequilibrium DMFT to analyze how photoexcitation induces an insulator-metal transition in the Falicov-Kimball model, revealing a non-thermal transition driven by photo-carrier creation rather than heating.

Contribution

It extends DMFT to nonequilibrium periodic systems to demonstrate the photoinduced insulator-metal transition mechanism in correlated electrons.

Findings

Growth of Drude-like peak at photon energy ~ U indicating metallic state

Band gap remains intact during transition, non-monotonic distribution function observed

Transition driven by photo-carrier creation, not thermal heating

Abstract

We investigate a photoinduced insulator-metal transition in the Falicov-Kimball model with the dynamical mean-field theory (DMFT) extended to nonequilibrium systems in periodic modulations in time. When the photon energy of the pump light is $\Omega \approx U$ ($U$: the interaction strength), a Drude-like peak is found to grow in the optical conductivity spectrum, which is an evidence that the system is driven into a metallic state. During the transition, the band gap does not collapse, whereas the distribution function exhibits a non-monotonic behaviour away from the Fermi distribution. This indicates that the transition cannot be accounted for by heating effects, but creation of photo-carriers is responsible.