Dispersions and magnetism of strain-induced pseudo Landau levels in Bernal-stacked bilayer graphene

TL;DR

This paper demonstrates that strain can induce Landau levels and magnetism in Bernal-stacked bilayer graphene, extending the concept from massless to massive excitations and revealing potential for strain-controlled magnetic properties.

Contribution

It analytically derives the dispersions of strain-induced pseudo Landau levels in bilayer graphene and shows how strain can tune magnetic order in this system.

Findings

Strain induces pseudo Landau levels in bilayer graphene.

The zeroth and first pseudo Landau levels are dispersionless and sublattice-polarized.

Interaction on these levels leads to antiferromagnetic order.

Abstract

Elastic strain can displace the massless Dirac fermions in monolayer graphene in a space-dependent fashion, similar to the effect of an external magnetic field, thus giving rise to Landau quantization. We here show that the strain-induced Landau quantization can also take place in Bernal-stacked bilayer graphene, where the low-energy excitations are massive rather than Dirac-like. The zigzag ribbon of Bernal-stacked bilayer graphene realizes a two-legged Su-Schrieffer-Heeger model with a domain wall, which coincides with the guiding center of the strain-induced pseudo Landau levels. We reduce the lattice model of the ribbon in the vicinity of the guiding center into an exactly solvable coupled Dirac model and analytically derive the dispersions of the strain-induced pseudo Landau levels. Remarkably, the zeroth and first pseudo Landau levels are dispersionless and sublattice-polarized. We elucidate that the interaction on these two pseudo Landau levels results in a global antiferromagnetic order. Our study extends the strain-induced Landau quantization to the massive excitations and indicates strain as a tuning knob of magnetism.