Ultrafast collinear scattering and carrier multiplication in graphene

TL;DR

This paper investigates ultrafast electron-electron interactions in graphene, revealing collinear scattering and Auger processes that enhance carrier multiplication, with implications for optoelectronic device performance.

Contribution

It combines high-resolution pump-probe spectroscopy with microscopic theory to elucidate the fundamental ultrafast scattering mechanisms in graphene.

Findings

Ultrafast collinear scattering enables Auger processes in graphene.

Carrier multiplication occurs during early relaxation stages.

Insights can improve photodetector efficiency.

Abstract

Graphene is emerging as a viable alternative to conventional optoelectronic, plasmonic, and nanophotonic materials. The interaction of light with carriers creates an out-of-equilibrium distribution, which relaxes on an ultrafast timescale to a hot Fermi-Dirac distribution, that subsequently cools via phonon emission. Here we combine pump-probe spectroscopy, featuring extreme temporal resolution and broad spectral coverage, with a microscopic theory based on the quantum Boltzmann equation, to investigate electron-electron collisions in graphene during the very early stages of relaxation. We identify the fundamental physical mechanisms controlling the ultrafast dynamics in graphene, in particular the significant role of ultrafast collinear scattering, enabling Auger processes, including charge multiplication, key to improving photovoltage generation and photodetectors.