Symmetry-protected coherent transport for diluted vacancies and adatoms in graphene

TL;DR

This paper investigates how certain symmetries in impurities like vacancies and adatoms in graphene influence electron transport, revealing symmetry-protected decoupling effects that suppress impurity scattering under specific conditions.

Contribution

It demonstrates that symmetry considerations can protect certain impurities from contributing to resistivity, providing new insights into impurity effects in graphene transport.

Findings

VAC impurities decouple from Dirac states at charge neutrality.

HS impurities decouple from entire momentum sets, reducing resistivity.

Symmetry protection persists across various impurity models.

Abstract

We study the effects of a low concentration of adatoms or single vacancies in the linear-response transport properties of otherwise clean graphene. These impurities were treated as localized orbitals, and for each type two cases with distinct coupling symmetries were studied. For adatoms, we considered top- and hollow-site adsorbates (TOP and HS). For vacancies, we studied impurity formation by soft bond reconstruction (REC), as well as the more symmetric case of charge accumulation in unreconstructed vacancies (VAC). Our results indicate that the transport is determined by usual impurity scattering when the graphene-impurity coupling does not possess $C_{3v}$ symmetry (TOP and REC). In contrast, VAC impurities decouple from the electronic states at the Dirac points, and yield no contribution to the resistivity for a sample in charge neutrality. Furthermore, the inversion-symmetry-conserving HS impurities also decouple from entire sets of momenta throughout the Brillouin zone, and do not contribute to the resistivity within a broad range of parameters. These behaviors are protected by $C_{3v}$ and inversion symmetry, respectively, and persist for more general impurity models.