Competing orders in bilayer graphene at charge neutrality

Rahul Nandkishore, MIT.

Abstract: We will discuss various interaction induced ordered phases in bilayer graphene. I will show that bilayer graphene in the absence of magnetic field shows an instability to a gapped excitonic state, whereas bilayer graphene in the presence of a magnetic field spontaneously orders ferromagnetically in the zeroth Landau level. I discuss the interplay between excitonic and ferromagnetic orders. I will show that a transverse magnetic field confines the Coulomb interaction in bilayer graphene into the plane, and will show that this enables us to reconcile the conflicting predictions of excitonic order and quantum hall ferromagnetism. I will conclude by discussing the probable phase diagram of bilayer graphene.