Coulomb interaction effects in graphene bilayers: electron-hole pairing and plasmaron formation

TL;DR

This paper presents a theoretical analysis of electron-electron interactions in double-layer graphene, revealing potential excitonic instabilities and plasmaron formation due to many-body effects under applied voltage.

Contribution

It introduces a projector-based renormalization approach to study how voltage-induced electron-hole pairing and plasmaron features emerge in bilayer graphene.

Findings

Electron-hole pairs can form under finite voltage difference.

An excitonic instability may occur at very low temperatures.

Charge carriers strongly interact with plasmons, producing broad plasmaron peaks.

Abstract

We report a theoretical study of the many-body effects of electron-electron interaction on the ground-state and spectral properties of double-layer graphene. Using a projector-based renormalization method we show that if a finite voltage difference is applied between the graphene layers electron-hole pairs can be formed and---at very low temperatures---an excitonic instability might emerge in a double-layer graphene structure. The single-particle spectral function near the Fermi surface exhibits a prominent quasiparticle peak, different from neutral (undoped) graphene bilayers. Away from the Fermi surface, we find that the charge carriers strongly interact with plasmons, thereby giving rise to a broad plasmaron peak in the angle-resolved photoemission spectrum.