Compressibility Instability of Interacting Electrons in Bilayer Graphene

TL;DR

This paper investigates how electron interactions in bilayer graphene lead to compressibility instability, especially when an energy gap is introduced, revealing conditions for system stability and instability.

Contribution

It demonstrates the impact of an externally tunable energy gap on the compressibility and stability of electrons in bilayer graphene using Hartree-Fock approximation.

Findings

Homogeneous system stable at zero gap

Negative compressibility at finite gap and low doping

Phase diagram of stability regions

Abstract

Using the self-consistent Hartree-Fock approximation, we study the compressibility instability of the interacting electrons in bilayer graphene. The chemical potential and the compressibility of the electrons can be significantly altered by an energy gap (tunable by external gate voltages) between the valence and conduction bands. For zero gap case, we show that the homogeneous system is stable. When the gap is finite, the compressibility of the electron system becomes negative at low carrier doping concentrations and low temperature. The phase diagram distinguishing the stable and unstable regions of a typically gapped system in terms of temperature and doping is also presented.