Isospin and momentum polarized orders in bilayer graphene

TL;DR

This paper predicts novel coexisting spin/valley isospin magnetism and momentum-polarized phases in bilayer graphene, which lead to unique ground state currents and anomalous Hall effects due to Berry curvature interactions.

Contribution

It introduces the concept of momentum-polarized phases and their coexistence with isospin magnetism in bilayer graphene, revealing new physical phenomena.

Findings

Coexistence of spin/valley isospin magnetism and momentum polarization.

Spontaneous displacement of electron momentum distribution.

Persistent ground state currents and anomalous Hall effects.

Abstract

Electron bands in the untwisted bilayer graphene flatten out in a transverse electric field, offering a promising platform for correlated electron physics. We predict that the spin/valley isospin magnetism, resembling that seen in moir\'{e} bands, coexists with momentum-polarized phases occurring via a ``flocking transition'' in momentum space. This transition results in the electron momentum distribution being spontaneously displaced relative to the $K$ and $K'$ valley centers. These phases feature unusual observables such as persistent currents in the ground state. Momentum-polarized carriers ``sample'' the Berry curvature of the conduction band, resulting in a unique behavior of the anomalous Hall conductivity and other effects that do not occur in previously studied systems.