Strained bilayer graphene: Band structure topology and Landau level spectrum

TL;DR

This paper investigates how mechanical strain in bilayer graphene alters its band topology, induces Lifshitz transitions, and impacts Landau levels and quantum Hall phenomena.

Contribution

It reveals the critical dependence of bilayer graphene's band topology on strain and details the resulting Lifshitz transition and its effects on electronic spectra.

Findings

Strain causes splitting of parabolic bands into Dirac cones.

Lifshitz transition occurs at intermediate energies.

Landau level spectra are significantly affected by strain.

Abstract

We show that topology of the low-energy band structure in bilayer graphene critically depends on mechanical deformations of the crystal which may easily develop in suspended graphene flakes. We describe the Lifshitz transition that takes place in strained bilayers upon splitting the parabollic bands at intermediate energies into several Dirac cones at the energy scale of few meV. Then, we show how this affects the electron Landau level spectra and the quantum Hall effect.