Gauge fields from strain in graphene

TL;DR

This paper revises the tight binding model for strained graphene, revealing additional geometric couplings and clarifying the nature of pseudomagnetic fields, which are not present independently of lattice deformation parameters.

Contribution

It introduces extra material-independent couplings in the continuum limit of strained graphene, highlighting their geometric origin and impact on electronic properties.

Findings

Extra couplings arise beyond standard hopping modifications.

No beta-independent pseudomagnetic fields exist in strained graphene.

A new vector field affects the electronic structure but does not behave as a gauge field.

Abstract

We revise the tight binding approach to strained or curved graphene in the presence of external probes such as Photoemission or Scanning Tunneling Microscopy experiments. We show that extra terms arise in the continuum limit of the tight binding Hamiltonian which can not be accounted for by changes in the hopping parameters due to lattice deformations, encoded in the parameter \beta. These material independent extra couplings are of the same order of magnitude as the standard ones and have a geometric origin. They include corrections to the position-dependent Fermi velocity and to a new vector field. We show that the new vector field does not couple to electrons like a standard gauge field and that no ? \beta-independent pseudomagnetic fields exist in strained graphene.