Fingerprints of a position-dependent Fermi velocity on scanning tunnelling spectra of strained graphene

TL;DR

This paper investigates how nonuniform strain in graphene causes position-dependent Fermi velocities, affecting local density of states and scanning tunnelling spectra, with analytical models clarifying previous approximations.

Contribution

It provides analytical expressions for the LDOS in strained graphene with position-dependent Fermi velocity, correcting prior simplified models and enhancing understanding of strain effects.

Findings

Analytical expressions match tight-binding calculations for LDOS variations.

Strain-induced anisotropy significantly impacts Fermi velocity and spectra.

Results applicable to strained graphene under magnetic fields.

Abstract

Nonuniform strain in graphene induces a position dependence of the Fermi velocity, as recently demonstrated by scanning tunnelling spectroscopy experiments. In this work, we study the effects of a position-dependent Fermi velocity on the local density of states (LDOS) of strained graphene, without and with the presence of a uniform magnetic field. The variation of LDOS obtained from tight-binding calculations is successfully explained by analytical expressions derived within the Dirac approach. These expressions also rectify a rough Fermi velocity substitution used in the literature that neglects the strain-induced anisotropy. The reported analytical results could be useful for understanding the nonuniform strain effects on scanning tunnelling spectra of graphene, as well as when it is exposed to an external magnetic field.