Impurity cyclotron resonance of anomalous Dirac electrons in graphene

TL;DR

This paper explores the unique impurity cyclotron resonances in graphene caused by localized potentials, revealing anomalous boundstates with distinctive optical properties and analyzing many-body effects on their optical conductivity.

Contribution

It uncovers the formation of anomalous boundstates in graphene's localized potentials and examines their optical matrix elements and many-body interactions.

Findings

Anomalous boundstates have sharp peaks inside and broad peaks outside the potential.

Optical matrix elements of anomalous states are unusually small and magnetic field sensitive.

Excited electron-hole pairs from anomalous states are nearly uncorrelated, with notable exchange effects.

Abstract

We have investigated a new feature of impurity cyclotron resonances common to various localized potentials of graphene. A localized potential can interact with a magnetic field in an unexpected way in graphene. It can lead to formation of anomalous boundstates that have a sharp peak with a width $R$ in the probability density inside the potential and a broad peak of size magnetic length $\ell$ outside the potential. We investigate optical matrix elements of anomalous states, and find that they are unusually small and depend sensitively on magnetic field. The effect of many-body interactions on their optical conductivity is investigated using a self-consistent time-dependent Hartree-Fock approach (TDHFA). For a completely filled Landau level we find that an excited electron-hole pair, originating from the optical transition between two anomalous impurity states, is nearly uncorrelated with other electron-hole pairs, although it displays a substantial exchange self-energy effects. This absence of correlation is a consequence of a small vertex correction in comparison to the difference between renormalized transition energies computed within the one electron-hole pair approximation. However, an excited electron-hole pair originating from the optical transition between a normal and an anomalous impurity states can be substantially correlated with other electron-hole states with a significant optical strength.