Creation and control of valley currents in graphene by few cycle light pulses

TL;DR

This paper demonstrates that few cycle THz light pulses can generate and manipulate fully valley-polarized currents in graphene, enabling potential applications in THz valleytronics through control of pulse properties.

Contribution

It introduces a method to create and control valley currents in graphene using few cycle THz pulses, highlighting a new approach for valleytronics in gapless or gapped systems.

Findings

100% valley polarized current achieved in graphene

Light wave control over current magnitude and direction

Global carrier envelope phase influences current control

Abstract

Well established for the visible spectrum gaps of the transition metal dichalcogenide family, valleytronics - the control of valley charge and current by light - is comparatively unexplored for the THz gaps that characterize graphene and topological insulators. Here we show that few cycle pulses of THz light can create and control a 100% valley polarized current in graphene, with light wave control over the current magnitude and direction. The latter is equal to an emergent pulse property of few cycle circularly polarized pulses, the "global" carrier envelope phase. Our findings both highlight the richness of few cycle light pulses in control over quantum matter, and provide a route towards a "THz valleytronics" in meV gapped systems.