Optical conductivity of disordered graphene beyond the Dirac cone approximation

Abstract

In this paper we systemically study the optical conductivity and density of states of disordered graphene beyond the Dirac cone approximation. The optical conductivity of graphene is computed by using the Kubo formula, within the framework of a full π -band tight-binding model. Different types of noncorrelated and correlated disorder are considered, such as random or Gaussian potentials, random or Gaussian nearest-neighbor hopping parameters, randomly distributed vacancies or their clusters, and randomly adsorbed hydrogen atoms or their clusters. For a large enough concentration of resonant impurities, an additional peak in the optical conductivity is found, associated with transitions between the midgap states and the Van Hove singularities of the main π band. We further discuss the effect of doping on the spectrum, and find that small amounts of resonant impurities are enough to obtain a background contribution to the conductivity in the infrared part of the spectrum, in agreement with recent experiments.

Screening and plasmons in pure and disordered single- and bilayer black phosphorus

“…Within the TB model, it can be considered as a correlated Gaussian potential [34,42,43], such that the potential at site i follows…”

Optical transmittance of multilayer graphene

“…-In order to obtain more reliable theoretical results of optical conductivity by considering the interlayer hoppings as well as different stacking sequence in multilayer graphene, we carried out the large-scale simulation in the framework of full  band tight-binding model. The optical conductivity G() is calculated numerically by using the Kubo formula [10][11][12] (omitting Drude weight which is not related to the light adsorption at finite ω), (4) where A is the sample area,  is the inverse temperature, is the FermiDirac function of the Hamiltonian operator H,  is the chemical potential, and J is the current operator. The state  is a normalized random state which covers all the eigenstates in the whole spectrum.…”

Fingerprints of disorder source in graphene

“…, where T k , d t , and p t have similar meanings as in LRDP, and we choose t = 0.25t and d t = 5a [26]. We want to emphasize that, although the amplitude ( ) and radius (d) of the Gaussian profile in the LRDH and LRDP are free parameters that can be turned in the tight-binding model, the numerical results show little quantitative difference as long as these parameters are of the same order as the chosen values.…”

“…For doped pristine graphene with nonzero chemical potential μ F , the optical conductivity is a step function σ (ω) = σ 0 (ω − 2μ F ) at zero temperature due to Pauli's exclusion principle. However, there are experimentally observed background contributions to the optical spectroscopy between 0 < ω < 2μ F [14,15], * s.yuan@science.ru.nl which are due to the extra intraband excitations introduced by disorder or many-body effects [14,[16][17][18][19][20][21][22][23][24][25][26] . This opens the possibility to identify the source of disorder via the optical measurements.…”