Unconventional scanning tunneling conductance spectra for graphene

TL;DR

This paper analyzes the tunneling conductance spectra of graphene using STM, revealing how impurity position and pseudospin symmetry influence the spectra, and proposes experimental tests for these theoretical predictions.

Contribution

It introduces a theoretical framework linking impurity position and pseudospin symmetry to unconventional STM spectra in graphene.

Findings

For undoped graphene, the conductance derivative relates to the tip's density of states.

Impurity position qualitatively affects the STM spectra shape.

Theoretical predictions suggest specific experimental tests.

Abstract

We compute the tunneling conductance of graphene as measured by a scanning tunneling microscope (STM) with a normal/superconducting tip. We demonstrate that for undoped graphene with zero Fermi energy, the first derivative of the tunneling conductance with respect to the applied voltage is proportional to the density of states of the STM tip. We also show that the shape of the STM spectra for graphene doped with impurities depends qualitatively on the position of the impurity atom in the graphene matrix and relate this unconventional phenomenon to the pseudopsin symmetry of the Dirac quasiparticles in graphene. We suggest experiments to test our theory.