Photo-induced Dynamics of Quasicrystalline Excitonic Insulator

TL;DR

This study investigates how a single-cycle electric pulse affects the excitonic insulator state in a quasicrystalline Penrose tiling, revealing different behaviors in BCS and BEC regimes and unique oscillations in the BEC regime.

Contribution

It provides the first analysis of photo-induced excitonic dynamics in a quasicrystalline lattice using real-space mean-field methods.

Findings

Excitonic order decreases in BCS regime after pulse.

Excitonic order increases in BEC regime after pulse.

Unique site-specific oscillations occur in the BEC regime.

Abstract

We study the photo-induced dynamics of the excitonic insulator in the two-band Hubbard model on the Penrose tiling by means of the time-dependent real-space mean-field approximation. We show that, with a single-cycle electric-field pulse, the bulk (spatially averaged) excitonic order parameter decreases in the BCS regime, while it increases in the BEC regime. To clarify the dynamics peculiar to the Penrose tiling, we examine the coordination number dependence of observables and analyze the perpendicular space. In the BEC regime, characteristic oscillations of the electron number at each site are induced by the pulse, which are not observed in normal crystals. On the other hand, the dynamics in the BCS regime is characterized by drastic change in the spatial pattern of the excitonic order parameter.