Direct Access to Auger recombination in Graphene

TL;DR

This paper presents a novel ultrafast microscopy technique that provides direct evidence of Auger recombination in graphene occurring within 10 femtoseconds, revealing detailed charge carrier dynamics at all energies and momenta.

Contribution

The study introduces a new experimental setup enabling direct observation of Auger recombination in graphene, a process previously only inferred indirectly.

Findings

Direct observation of Auger recombination in graphene

Recombination occurs on a sub-10 femtosecond timescale

Energy- and momentum-resolved carrier populations identified

Abstract

Auger scattering channels are of fundamental importance to describe and understand the non-equilibrium charge carrier dynamics in graphene. While impact excitation increases the number of carriers in the conduction band and has been observed experimentally, direct access to its inverse process, Auger recombination, has so far been elusive. Here, we tackle this problem by applying our novel setup for ultrafast time-resolved photoelectron momentum microscopy. Our approach gives simultaneous access to charge carrier dynamics at all energies and in-plane momenta within the linearly dispersive Dirac cones. We thus provide direct evidence for Auger recombination on a sub-10~fs timescale by identifying transient energy- and momentum-dependent populations far above the excitation energy. We compare our results with model calculations of scattering processes in the Dirac cone to support our experimental findings.