Fermi Velocity Enhancement in Monolayer and Bilayer Graphene

TL;DR

This paper compares how electron interactions affect the Fermi surface effective mass in monolayer and bilayer graphene, revealing different behaviors at low carrier densities.

Contribution

It provides a comparative analysis explaining why the effective mass vanishes in monolayer but remains finite in bilayer graphene at low densities.

Findings

Effective mass vanishes in monolayer graphene at low density.

Effective mass remains finite but suppressed in bilayer graphene.

Interband exchange interactions influence Fermi surface properties.

Abstract

In single-layer graphene sheets non-local interband exchange leads to a renormalized Fermi-surface effective mass which vanishes in the low carrier-density limit. We report on a comparative study of Fermi surface effective mass renormalization in single-layer and AB-stacked bilayer graphene. We explain why the mass does not approach zero in the bilayer case, although its value is still strongly suppressed.