Band dispersion of graphene with structural defects

Piotr Kot,Christian R Ast,Carola Straßer,Sina Habibian,Pavel M Ostrovsky,Jonathan Parnell

doi:10.1103/physrevb.101.235116

Piotr Kot, Christian R Ast + Show 4 more

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https://doi.org/10.1103/physrevb.101.235116

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Abstract

We study the band dispersion of graphene with randomly distributed structural defects using two complementary methods, exact diagonalization of the tight-binding Hamiltonian and implementing a self-consistent T matrix approximation. We identify three distinct types of impurities resulting in qualitatively different spectra in the vicinity of the Dirac point. First, resonant impurities, such as vacancies or 585 defects, lead to stretching of the spectrum at the Dirac point with a finite density of localized states. This type of spectrum has been observed in epitaxial graphene by photoemission spectroscopy and discussed extensively in the literature. Second, nonresonant (weak) impurities, such as paired vacancies or Stone-Wales defects, do not stretch the spectrum but provide a line broadening that increases with energy. Finally, disorder that breaks sublattice symmetry, such as vacancies placed in only one sublattice, open a gap around the Dirac point and create an impurity band in the middle of this gap. We find good agreement between the results of the two methods and also with the experimentally measured spectra.

Highlights

Graphene has presented high potential for providing the generation of electronic materials due to its strictly two-dimensional character as well as its high electron mobility
We study the band dispersion of graphene with randomly distributed structural defects using two complementary methods, exact diagonalization of the tight-binding Hamiltonian and implementing a self-consistent T matrix approximation
We present a real-space tight-binding calculation modeling different kinds of structural defects randomly distributed over a graphene sample

Summary

Introduction

Graphene has presented high potential for providing the generation of electronic materials due to its strictly two-dimensional character as well as its high electron mobility. It has demonstrated high design flexibility, such as doping by atoms or molecules, efficient decoupling from an underlying substrate, or high tensile strength for flexible electronics [1,2,3], and has been the catalyst for the creation of new fields of study such as two-dimensional materials or Dirac semimetals [4,5,6,7,8,9,10]. In order to open a band gap, this sublattice symmetry has to be broken

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