Effect of impurities in high-symmetry lattice positions on the local density of states and conductivity of graphene

TL;DR

This paper investigates how different impurity positions in graphene affect its local electronic properties, bound states, and conductivity, providing insights relevant for interpreting scanning tunneling spectroscopy and understanding impurity effects.

Contribution

It offers a semi-analytical analysis of impurity effects on LDOS, bound states, and conductivity in graphene, considering various impurity positions and their impact on electronic properties.

Findings

Impurities induce bound states at specific energies depending on their position.

The local density of states varies significantly near impurities, affecting electronic behavior.

Conductivity exhibits a sublinear dependence on carrier concentration due to impurities.

Abstract

Motivated by quantum chemistry calculations, showing that molecular adsorption in graphene takes place on preferential sites of the honeycomb lattice, we study the effect of an isolated impurity on the local electronic properties of a graphene monolayer, when the impurity is located on a site-like, bond-like, or hollow-like position. We evaluate the local density of states (LDOS) as a function of energy on the impurity and on its neighboring sites, as well as in reciprocal space, at an energy corresponding to a bound state, in the three cases of interest. The latter study may be relevant to interpret the results of Fourier transformed scanning tunneling spectroscopy, as they show which states mostly contribute to impurity-induced variations of the LDOS. We also estimate, semi-analytically, the dependence of the condition for having a low-energy bound state on the impurity potential strength and width. Such results are then exploited to obtain the quasiparticle lifetime and the static conductivity in graphene in the dilute impurity limit. In particular, we recover a sublinear dependence of the conductivity on the carrier concentration as a generic impurity effect.