Photoexcitation Cascade and Quantum-Relativistic Jets in Graphene

TL;DR

This paper reveals how many-body effects unblock electron-hole pair production in graphene, leading to relativistic-jet-like emission of secondary carriers, which enhances carrier multiplication in photoexcited Dirac materials.

Contribution

It uncovers the role of off-shell many-body interactions in enabling carrier cascades and jet-like emissions in graphene, a novel insight into photoexcitation dynamics.

Findings

Unblocked electron-hole decay pathways due to many-body effects.

Observation of sharp angular distribution of secondary carriers resembling jets.

Carrier multiplication of up to ten secondary carriers per photon.

Abstract

In Dirac materials linear band dispersion blocks momentum-conserving interband transitions, creating a bottleneck for electron-hole pair production and carrier multiplication in the photoexcitation cascade. Here we show that the decays are unblocked and the bottleneck is relieved by subtle many-body effects involving multiple off-shell e-h pairs. The decays result from a collective behavior due to emission of many soft pairs. We discuss characteristic signatures of the off-shell pathways, in particular the sharp angular distribution of secondary carriers, resembling relativistic jets in high-energy physics. The jets can be directly probed using solid-state equivalent of particle detectors. Collinear scattering enhances carrier multiplication, allowing for emission of as many as ${\sim}10$ secondary carriers per single absorbed photon.