Photoinduced metallization of excitonic insulators
Satoshi Ejima, F. F. Lange, Holger Fehske
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 they decrease over time. This implies the possible metallization of ${\mathrm{Ta}}_{2}\mathrm{Ni}{\mathrm{Se}}_{5}$, 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 ${\mathrm{Ta}}_{2}\mathrm{Ni}{\mathrm{Se}}_{5}$.