Effects of strain on electronic properties of graphene

TLDR

The study uses first‑principles calculations to examine how uniaxial and isotropic strain affect graphene’s electronic properties. The calculations show that graphene remains semi‑metallic up to 30 % uniaxial strain (except a narrow gap‑opening range), that the parallel Fermi velocity drops to zero while the perpendicular one rises by up to 25 %, that low‑energy behavior follows a generalized Weyl equation with coexisting massless and massive carriers, and that strain raises the work function, effectively acting as an electronic scalar potential.

Abstract

We present first-principles calculations of electronic properties of graphene under uniaxial and isotropic strains, respectively. The semi-metallic nature is shown to persist up to a very large uniaxial strain of 30% except a very narrow strain range where a tiny energy gap opens. As the uniaxial strain increases along a certain direction, the Fermi velocity parallel to it decreases quickly and vanishes eventually, whereas the Fermi velocity perpendicular to it increases by as much as 25%. Thus, the low energy properties with small uniaxial strains can be described by the generalized Weyl's equation while massless and massive electrons coexist with large ones. The work function is also predicted to increase substantially as both the uniaxial and isotropic strain increases. Hence, the homogeneous strain in graphene can be regarded as the effective electronic scalar potential.