Electromagnetic properties of a double layer graphene system with electron-hole pairing

TL;DR

This paper investigates how electron-hole pairing in double layer graphene alters electromagnetic responses, revealing spectral modifications, plasmon spectrum changes, and new surface wave behaviors with potential optoelectronic implications.

Contribution

It provides the first detailed analysis of electromagnetic properties considering electron-hole pairing effects in double layer graphene systems.

Findings

Peak in reflection and absorption at the quasiparticle gap frequency

Splitting of optical TM mode into undamped and damped branches

Opening of a subgap frequency window for surface TE waves

Abstract

We study electromagnetic properties of a double layer graphene system in which electrons from one layer are coupled with holes from the other layer. The gauge invariant linear response functions are obtained. The frequency dependences of the transmission, reflection and absorption coefficients are computed. We predict a peak in the reflection and absorption at the frequency equals to the gap in the quasiparticle spectrum. It is shown that the electron-hole pairing results in an essential modification of the spectrum of surface TM plasmons. We find that the optical TM mode splits into a low frequency undamped branch and a high frequency damped branch. At zero temperature the lower branch disappears. It is established that the pairing does not influence the acoustic TM mode. It is also shown that the pairing opens the frequency window in the subgap range for the surface TE wave.