Nonequilibrium plasmon emission drives ultrafast carrier relaxation dynamics in photoexcited graphene

TL;DR

This paper reveals that nonequilibrium plasmon emission significantly accelerates carrier relaxation in photoexcited graphene, providing a new ultrafast pathway that complements phonon emission and explains the short-lived carrier inversion.

Contribution

It introduces plasmon emission as a key ultrafast relaxation mechanism in graphene, expanding understanding beyond phonon and Auger processes.

Findings

Plasmon emission converts carrier inversion into hot carriers rapidly.

Hot carriers' energy is subsequently extracted by optical phonons.

The mechanism explains the femtosecond lifetime of inversion in graphene.

Abstract

The fast decay of carrier inversion in photoexcited graphene has been attributed to optical phonon emission and Auger recombination. Plasmon emission provides another pathway that, as we show here, drives the carrier relaxation dynamics on ultrafast timescales. In studying the nonequilibrium relaxation dynamics we find that plasmon emission effectively converts inversion into hot carriers, whose energy is then extracted by optical phonon emission. This mechanism not only explains the observed fs-lifetime of inversion but also offers the prospect for atomically thin ultrafast plasmon emitters.