Time-resolved ARPES and optical transport properties of irradiated twisted bilayer graphene in steady-state

TL;DR

This paper explores how different non-equilibrium occupations of Floquet states in irradiated twisted bilayer graphene affect optical Hall conductivity, revealing near-quantized responses in steady-state conditions and non-quantized in projected occupations.

Contribution

It provides a theoretical analysis of the impact of steady-state versus projected Floquet occupations on optical transport in twisted bilayer graphene under periodic driving.

Findings

Steady-state occupation yields near-quantized optical Hall conductivity.

Projected occupation results in non-quantized optical Hall conductivity.

Different regimes can be distinguished experimentally in twisted bilayer graphene.

Abstract

We theoretically investigate the trARPES spectrum and optical Hall conductivity in periodically driven twisted bilayer graphene, considering both steady-state and "projected" occupations of the Floquet state. In periodically driven pre-thermalized systems, steady-state occupation of Floquet states is predicted to occur when coupled to a bath, while these states have projected occupation instantaneously after the driving starts. We study how these two regimes can give markedly different responses in optical transport properties. In particular, our results show that steady-state occupation leads to near-quantized optical Hall conductivity for a range of driving parameters in twisted bilayer graphene, whereas projected occupation leads to non-quantized values. We discuss the experimental feasibility of probing such non-equilibrium states in twisted bilayer graphene.