Chiral Wigner crystal phases induced by Berry curvature

TL;DR

This paper explores how Berry curvature influences Wigner crystal phases in bilayer graphene, revealing a new chiral WC state with spontaneous orbital angular momentum and potential chiral spin phases.

Contribution

It introduces a novel chiral Wigner crystal phase induced by Berry curvature and derives the phase boundary and effective Hamiltonian for spin ordering.

Findings

Berry curvature induces a chiral WC state with orbital angular momentum.

Phase boundary of WC depends on electron density and displacement field.

Chiral terms in the Hamiltonian can lead to chiral spin-density waves or spin liquids.

Abstract

We consider the impact of Berry phase on the Wigner crystal (WC) state of a two-dimensional electron system. We consider first a model of Bernal bilayer graphene with a perpendicular displacement field, and we show that Berry curvature leads to a new kind of WC state in which the electrons acquire a spontaneous orbital angular momentum when the displacement field exceeds a critical value. We determine the phase boundary of the WC state in terms of electron density and displacement field at low temperature. We then derive the general effective Hamiltonian that governs the ordering of the physical electron spin. We show that this Hamiltonian includes a chiral term that can drive the system into chiral spin-density wave or spin liquid phases. The phenomena we discuss are relevant for the valley-polarized Wigner crystal phases observed in multilayer graphene.