Photo-excited Carrier Dynamics and Impact Excitation Cascade in Graphene

TL;DR

This paper investigates how photo-excitation induces impact excitation cascades in graphene, revealing that the number of generated pairs depends on doping and energy, with specific signatures for experimental detection.

Contribution

It provides a detailed analysis of impact excitation cascades in graphene, highlighting the tunability by doping and energy scaling, which advances understanding of carrier dynamics.

Findings

Number of pair excitations depends strongly on doping

Excited pairs and cascade time scale linearly with excitation energy

Angular distribution of pair excitations is sharply peaked

Abstract

Photo-excitation in solids can trigger a cascade in which multiple particle-hole excitations are generated. We analyze the carrier multiplication cascade of impact excitation processes in graphene and show that the number of pair excitations has a strong dependence on doping, which makes carrier multiplication gate-tunable. We also predict that the number of excited pairs as well as the characteristic time of the cascade scale linearly with photo-excitation energy. These dependences, as well as sharply peaked angular distribution of pair excitations, provide clear experimental signatures of carrier multiplication.