Electric field control of spins in bilayer graphene: Local moment formation and local moment interactions

TL;DR

This paper investigates how electric fields influence local magnetic moments and their interactions in bilayer graphene, revealing the potential to control magnetism via external electric tuning.

Contribution

It introduces a mean-field analysis of impurity states in bilayer graphene, showing electric field control of local moments and their interactions, which is novel compared to prior studies.

Findings

Electric fields can turn local moments on or off in bilayer graphene.

The impurity phase diagram is significantly affected by electric field and chemical potential.

RKKY interactions between moments can be tuned by electric fields and doping.

Abstract

We study local moment formation for adatoms on bilayer graphene (BLG) within a mean-field theory of the Anderson impurity model. The wavefunctions of the BLG electrons induce strong particle-hole asymmetry and band dependence of the hybridization, which is shown to result in unusual features in the impurity model phase diagram. We also study the effect of varying the chemical potential, as well as varying an electric field perpendicular to the bilayer; the latter modifies the density of states of electrons in BLG and, more significantly, shifts the impurity energy. We show that this leads to regimes in the impurity phase diagram where local moments can be turned on or off by applying modest external electric fields. Finally, we show that the RKKY interaction between local moments can be varied by tuning the chemical potential (as has also been suggested in monolayer graphene) or, more interestingly, by tuning the electric field so that it induces changes in the band structure of BLG.