Functionalized Graphene in Quantizing Magnetic Field: The case of bunched impurities

TL;DR

This paper explores how bunched impurities in graphene under a magnetic field create hybridized impurity levels, significantly affecting the electronic spectrum and spin polarization, with implications for quantum Hall phenomena.

Contribution

It introduces the analysis of dense impurity clusters in graphene under magnetic fields, revealing their impact on electronic states and spin polarization, extending beyond uniform adatom coverage studies.

Findings

Impurity levels hybridize with Landau levels and split into two states.

Dense impurity clusters alter the local electron spectrum and spin polarization.

A surrounding electron droplet with an edge current is formed by impurity effects.

Abstract

Resonant scattering at the atomic absorbates in graphene was investigated recently in relation with the transport and gap opening problems. Attaching an impurity atom to graphene is believed to lead to the creation of unusual zero energy localized electron states. This paper aims to describe the behavior of the localized impurity-induced levels in graphene in a quantizing magnetic field. It is shown that in the magnetic field the impurity level effectively hybridizes with one of the n=0 Landau level states and splits into two opposite-energy states. The new hybridized state is doubly occupied, forming a spin-singlet and reducing the polarization of a Quantum Hall ferromagnet in undoped graphene. Taking into account the electron-electron interaction changes radically the spectrum of the electrons surrounding the impurity, which should be seen experimentally. While existing publications investigate graphene uniformly covered by adatoms, here we address a possibly even more experimentally relevant case of the clusterized impurity distribution. The limit of a dense bunch of the impurity atoms is considered, and it is shown, how such a bunch changes the spectrum and spin polarization of a large dense electron droplet surrounding it. The droplet is encircled by an edge state carrying a persistent current.