Photoinduced phase switching from Mott insulator to metallic state in the quarter-filled Peierls-Hubbard model

TL;DR

This study uses exact diagonalization to explore how ultrafast photoirradiation can induce a transition from an insulating to a metallic state in a one-dimensional quarter-filled Peierls-Hubbard model, revealing a novel charge carrier mechanism.

Contribution

It demonstrates a new photoinduced insulator-metal transition mechanism involving dimer charge carriers in the quarter-filled Peierls-Hubbard model.

Findings

Ultrafast photoirradiation enhances the Drude peak indicating metallicity.

Suppression of the Drude peak occurs with increasing Coulomb repulsion U.

Photoinduced charge carriers are identified as empty-occupied and double-occupied dimers.

Abstract

Utilizing the exact diagonalization method, we investigate the one-dimensional Peierls-Hubbard model at quarter filling, where it manifests as an antiferromagnetic Mott insulator in units of dimers. By increasing the on-site Coulomb repulsion U, we observe a significant suppression of the Drude peak, based on a nonequilibrium linear response theory capable of capturing the zero-frequency (Drude) weight of the optical conductivity under periodic boundary conditions. However, after the ultrafast photoirradiation of this model with large U, we detect a distinct enhancement of the Drude peak, signifying the onset of a photoinduced insulator-metal transition. Comparing these dynamics with the half-filled Hubbard model and a noninteracting spinless half-filled Su-Schrieffer-Heeger model (corresponding to the quarter-filled Peierls-Hubbard model with infinite U), we propose a novel mechanism for the photoinduced metallic state: the empty-occupied and double-occupied dimers serve as the photoinduced charge carriers, akin to the holons and doublons in Hubbard model.