# Multicomponent screening and superfluidity in gapped electron-hole double bilayer graphene with realistic bands

## TL;DR

This paper presents a comprehensive mean-field study of superfluidity in gapped electron-hole double bilayer graphene, emphasizing the effects of multiband structure and screening on pairing behavior.

## Contribution

It introduces a detailed model including intraband and interband screening, realistic band structure, and pair transfer effects, revealing superfluid confinement to the conduction band.

## Key findings

- Screening suppresses interband pair transfers.
- Superfluidity is confined to the conduction band despite small gaps.
- Interband contributions to screening remain unaffected.

## Abstract

Superfluidity has recently been reported in double electron-hole bilayer graphene. The multiband nature of the bilayers is important because of the very small band gaps between conduction and valence bands. The long range nature of the superfluid pairing interaction means that screening must be fully taken into account. We have carried out a systematic mean-field investigation that includes (i) contributions to screening from both intraband and interband excitations, (ii) the low-energy band structure of bilayer graphene with its small band gap and flattened Mexican hat-like low-energy bands, (iii) the large density of states at the bottom of the bands, (iv) electron-hole pairing in the multibands, and (v) electron-hole pair transfers between the conduction and valence band condensates. We find that the superfluidity strongly modifies the intraband contributions to the screening, but that the interband contributions are unaffected. Unexpectedly, the net effect of the screening is to suppress Josephson-like pair transfers and to confine the superfluid pairing entirely to the conduction band condensate even for very small band gaps, making the system behave similarly to a one-band superfluid.