Electronic states in a graphene flake strained by a Gaussian bump

TL;DR

This paper investigates the electronic states in a graphene flake with a Gaussian bump strain, revealing significant deviations from traditional models and highlighting strain-induced confinement and sublattice localization.

Contribution

It provides a detailed analysis of the pseudo-magnetic field and electronic states in a realistically strained graphene flake, extending beyond small-strain approximations.

Findings

Pseudo-magnetic field differs from tight-binding results at high strain.

Six-fold symmetry of wave functions relates to strain effects along graphene directions.

Electrons are confined and localized on a single sublattice in the strained region.

Abstract

The effect of strain in graphene is usually modeled by a pseudo-magnetic vector potential which is, however, derived in the limit of small strain. In realistic cases deviations are expected in view of graphene's very high strain tolerance, which can be up to 25%. Here we investigate the pseudo-magnetic field generated by a Gaussian bump and we show that it exhibits significant differences with numerical tight-binding results. Furthermore, we calculate the electronic states in the strained region for a hexagon shaped flake with armchair edges. We find that the six-fold symmetry of the wave functions inside the Gaussian bump is directly related to the different effect of strain along the fundamental directions of graphene: zigzag and armchair. Low energy electrons are strongly confined in the armchair directions and are localized on the carbon atoms of a single sublattice.