Exciton formation in graphene bilayer

TL;DR

This paper investigates exciton formation in graphene bilayers, demonstrating a critical Coulomb interaction strength necessary for exciton instability, influenced by voltage difference and inter-layer hopping.

Contribution

It derives and solves self-consistent exciton gap equations, revealing the conditions for exciton formation in bilayer graphene with finite voltage.

Findings

Existence of a critical Coulomb interaction strength for exciton formation

Dependence of critical strength on voltage difference

Analytical and numerical solutions of gap equations

Abstract

Exciton instability in graphene bilayer systems is studied in the case of a short-ranged Coulomb interaction and a finite voltage difference between the layers. Self-consistent exciton gap equations are derived and solved numerically and analytically under controlled approximation. We obtain that a critical strength of the Coulomb interaction exists for the formation of excitons. The critical strength depends on the amount of voltage difference between the layers and on the inter-layer hopping parameter.