Nonlinear electric conductivity and THz-induced charge transport in graphene

TL;DR

This paper investigates the nonlinear electric conductivity of graphene under static electric fields and explores ultrafast charge transport induced by THz pulses, revealing complex field-dependent behaviors and tunneling effects.

Contribution

It introduces a quantum master equation approach to analyze nonlinear conductivity and demonstrates ultrafast charge control using few-cycle THz pulses in graphene.

Findings

Conductivity initially suppressed with increasing field strength

Conductivity increases beyond 1 MV/m due to Landau--Zener tunneling

Ultrafast charge transport can be controlled with THz pulses

Abstract

Based on the quantum master equation approach, the nonlinear electric conductivity of graphene is investigated under static electric fields for various chemical potential shifts. The simulation results show that, as the field strength increases, the effective conductivity is firstly suppressed, reflecting the depletion of effective carriers due to the large displacement in the Brillouin zone caused by the strong field. Then, as the field strength exceeds $1$~MV/m, the effective conductivity increases, overcoming the carrier depletion via the Landau--Zener tunneling process. Based on the nonlinear behavior of the conductivity, the charge transport induced by few-cycle THz pulses is studied to elucidate the ultrafast control of electric current in matter.