Light-field driven currents in graphene

TL;DR

This paper demonstrates that monolayer graphene can exhibit light-field-driven electron dynamics, including residual currents, driven by ultrafast laser pulses, revealing quantum interference effects on femtosecond timescales in a metallic system.

Contribution

It uncovers coherent light-field-driven electron dynamics in graphene, a metal, on femtosecond timescales, expanding understanding of ultrafast processes in metallic materials.

Findings

Residual conduction current controlled by light waveform

Electron quantum-path interference identified as key mechanism

Dynamics occur faster than electron-electron and electron-phonon scattering

Abstract

Ultrafast electron dynamics in solids under strong optical fields has recently found particular attention. In dielectrics and semiconductors, various light-field-driven effects have been explored, such as high-harmonic generation, sub-optical-cycle interband population transfer and nonperturbative increase of transient polarizability. In contrast, much less is known about field-driven electron dynamics in metals because charge carriers screen an external electric field in ordinary metals. Here we show that atomically thin monolayer Graphene offers unique opportunities to study light-field-driven processes in a metal. With a comparably modest field strength of up to 0.3 V/{\AA}, we drive combined interband and intraband electron dynamics, leading to a light-field-waveform controlled residual conduction current after the laser pulse is gone. We identify the underlying pivotal physical mechanism as electron quantum-path interference taking place on the 1-femtosecond ($10^{-15}$ second) timescale. The process can be categorized as Landau-Zener-St\"uckelberg interferometry. These fully coherent electron dynamics in graphene take place on a hitherto unexplored timescale faster than electron-electron scattering (tens of femtoseconds) and electron-phonon scattering (hundreds of femtoseconds). These results broaden the scope of light-field control of electrons in solids to an entirely new and eminently important material class -- metals -- promising wide ramifications for band structure tomography and light-field-driven electronics.