Critical behavior for point monopole and dipole electric impurities in uniformily and uniaxially strained graphene

TL;DR

This paper analyzes how uniform and uniaxial strain in graphene affects the critical behavior of bound states caused by point electric monopole and dipole impurities, revealing strain-dependent promotion or inhibition of phenomena like atomic collapse and Efimov-like scaling.

Contribution

It provides an analytical solution to the Dirac equation in strained graphene with impurity potentials, showing how strain modifies critical impurity effects.

Findings

Strain direction influences atomic collapse thresholds.

Strain alters the conditions for Efimov-like bound state cascades.

Anisotropic Fermi velocity impacts impurity-induced bound states.

Abstract

We revisit the problem of bound states in graphene under the influence of point electric monopole and dipole impurity potentials extended to the case in which the membrane of this material is uniformly and uniaxially strained, which leads to a redefinition of the charge and dipole moment, respectively. By considering an anisotropic Fermi velocity, we analytically solve the resulting Dirac equation for each potential. We observe that the effect of the anisotropy is to promote or inhibit the critical behavior known to occur for each kind of impurity, depending on the direction along which strain is applied: both the atomic collapse, for the monopole impurity, and the emergence of cascades of infinitely many bound states with a universal Efimov-like scaling, for the dipole impurity, are phenomena that occur under less or more restrictive conditions due to strain.