Soft pair excitations and double-log divergences due to carrier interactions in graphene

TL;DR

This paper investigates how strong carrier interactions in graphene lead to multiple soft electron-hole excitations during photoexcitation, resulting in double-log divergences and characteristic power-law spectra similar to QED phenomena.

Contribution

It demonstrates the generation of soft electron-hole pairs in graphene during photoexcitation, revealing double-log divergences and power-law spectra analogous to quantum electrodynamics effects.

Findings

Double-log divergence in soft pair emission rate

Power-law divergence in energy spectrum of soft pairs

Carrier interactions significantly enhance pair production

Abstract

Interactions between charge carriers in graphene lead to logarithmic renormalization of observables mimicking the behavior known in (3+1)-dimensional quantum electrodynamics (QED). Here we analyze soft electron-hole (e-h) excitations generated as a result of fast charge dynamics, a direct analog of the signature QED effect - multiple soft photons produced by the QED vacuum shakeup. We show that such excitations are generated in photon absorption, when a photogenerated high-energy e-h pair cascades down in energy and gives rise to multiple soft e-h excitations. This fundamental process is manifested in a double-log divergence in the emission rate of soft pairs and a characteristic power-law divergence in their energy spectrum of the form $\frac{1}{\omega}\ln \left(\frac{\omega}{\Delta}\right) $. Strong carrier-carrier interactions make pair production a prominent pathway in the photoexcitation cascade.