Anomalous Induced Density of Supercritical Coulomb Impurities in Graphene Under Strong Magnetic Fields

TL;DR

This paper explores how strong magnetic fields affect the behavior of supercritical Coulomb impurities in graphene, revealing anomalous density distributions, screening effects, and impurity resonances.

Contribution

It introduces a detailed analysis of the induced density structure and impurity states in graphene under strong magnetic fields, highlighting novel anomalous effects.

Findings

Induced density peaks can shift away from impurity centers.

Impurity charge is screened even with filled Landau impurity bands.

Anticrossing impurity states cause additional cyclotron resonances.

Abstract

The Coulomb impurity problem of graphene, in the absence of a magnetic field, displays discrete scale invariance. Applying a magnetic field introduces a new magnetic length scale $\ell$ and breaks discrete scale invariance. Moreover, a magnetic field is a singular perturbation as it turns complex energies into real energies. Nonetheless, the Coulomb potential must be regularized with a length $R$ at short distances for supercritical impurities. We investigate the structure of the induced density of a filled Landau impurity band in the supercritical regime. The coupling between Landau level states by the impurity potential is nontrivial and can lead to several anomalous effects. First, we find that the peak in the induced density can be located away from the center of the impurity, depending on the characteristics of the Landau impurity bands. Second, the impurity charge is screened, despite the Landau impurity band being filled. Third, anticrossing impurity states lead to additional impurity cyclotron resonances.