Density of states in the bilayer graphene with the excitonic pairing interaction

TL;DR

This paper investigates how excitonic interactions influence the density of states in bilayer graphene, revealing excitonic shifts, asymmetries, and phase transitions related to excitonic coherence and condensation.

Contribution

It introduces a detailed analysis of excitonic effects on DOS in bilayer graphene, highlighting phase transitions and coherence phenomena not previously characterized.

Findings

Excitonic shift of the neutrality point occurs even without interactions.

Large interlayer hopping enhances excitonic coherence effects.

A phase transition from excitonic insulator to coherent condensate is identified.

Abstract

In the present paper, we consider the excitonic effects on the single particle normal density of states (DOS) in the bilayer graphene (BLG). The local interlayer Coulomb interaction is considered between the particles on the non-equivalent sublattice sites in different layers of the BLG. We show the presence of the excitonic shift of the neutrality point, even for the noninteracting layers. Furthermore, for the interacting layers, a very large asymmetry in the DOS structure is shown between the particle and hole channels. At the large values of the interlayer hopping amplitude, a large number of DOS at the Dirac's point indicates the existence of the strong excitonic coherence effects between the layers in the BLG and the enhancement of the excitonic condensation. We have found different competing orders in the interacting BLG. Particularly, a phase transition from the hybridized excitonic insulator phase to the coherent condensate state is shown at the small values of the local interlayer Coulomb interaction.