Photoinduced metallization of excitonic insulators

TL;DR

This study uses advanced numerical techniques to demonstrate how photoirradiation can induce a transition from insulating to metallic states in excitonic insulators, specifically modeling Ta$_2$NiSe$_5$.

Contribution

It provides the first numerical evidence of photoinduced metallization in the extended Falicov-Kimball model, linking theoretical predictions with experimental observations.

Findings

Photoinduced insulator-to-metal transition observed in spectra.

Enhanced pair correlations during pulse irradiation.

Agreement with experimental photoemission data on Ta$_2$NiSe$_5$.

Abstract

Utilizing the time-dependent density-matrix renormalization group technique, we numerically prove photoinduced pairing states in the extended Falicov-Kimball model (EFKM) at half filling, both with and without internal SU(2) symmetry. In the time-dependent photoemission spectra an extra band appears above the Fermi energy after pulse irradiation, indicating an insulator-to-metal transition. Even in the absence of the SU(2) structure, the pair correlations are enhanced during the pump, and afterwards decrease over time. This implies the possible metallization of Ta$_2$NiSe$_5$, a strong candidate for an excitonic insulator material, for which the EFKM is considered to be the minimal theoretical model. Simulating the photoemission with optimized pulse parameters, we demonstrate a photoinduced quantum phase transition, in accord with recent findings in time- and angle-resolved photoemission spectroscopy experiments on Ta$_2$NiSe$_5$.