Berry Curvature Dipole in Strained Graphene: a Fermi Surface Warping Effect

TL;DR

This paper demonstrates that strain-induced Fermi surface warping in graphene can generate significant Berry curvature dipoles, even without spin-orbit coupling, expanding the understanding of topological effects in 2D materials.

Contribution

It reveals that Fermi surface warping in strained graphene induces Berry curvature dipoles without requiring spin-orbit coupling, a novel topological phenomenon.

Findings

Berry dipoles in strained graphene are comparable to those in transition metal dichalcogenides.

Fermi surface warping is the key factor for Berry dipole emergence in these systems.

Strain engineering can control topological properties in 2D materials.

Abstract

It has been recently established that optoelectronic and non-linear transport experiments can give direct access to the dipole moment of the Berry curvature in non-magnetic and non-centrosymmetric materials. Thus far, non-vanishing Berry curvature dipoles have been shown to exist in materials with substantial spin-orbit coupling where low-energy Dirac quasiparticles form tilted cones. Here, we prove that this topological effect does emerge in two-dimensional Dirac materials even in the complete absence of spin-orbit coupling. In these systems, it is the warping of the Fermi surface that triggers sizeable Berry dipoles. We show indeed that uniaxially strained monolayer and bilayer graphene, with substrate-induced and gate-induced band gaps respectively, are characterized by Berry curvature dipoles comparable in strength to those observed in monolayer and bilayer transition metal dichalcogenides.