Two-electron bound states near a Coulomb impurity in gapped graphene

TL;DR

This paper predicts the existence of a two-electron bound state near a Coulomb impurity in gapped graphene, using a variational approach to analyze the effects of weak electron-electron interactions.

Contribution

It introduces a variational Chandrasekhar-Dirac wave function to demonstrate bound states in gapped graphene with Coulomb impurities, providing a new method to probe electron interactions.

Findings

Existence of at least one bound state near Coulomb impurity in gapped graphene.

Bound state signatures are detectable via scanning tunneling microscopy.

Provides a way to measure electron-electron interaction strength in graphene.

Abstract

We formulate and solve the perhaps simplest two-body bound state problem for interacting Dirac fermions in two spatial dimensions. A two-body bound state is predicted for gapped graphene monolayers in the presence of weakly repulsive electron-electron interactions and a Coulomb impurity with charge $Ze>0$, where the most interesting case corresponds to $Z=1$. We introduce a variational Chandrasekhar-Dirac spinor wave function and show the existence of at least one bound state. This state leaves clear signatures accessible by scanning tunneling microscopy. One may thereby obtain direct information about the strength of electron-electron interactions in graphene.