Spatially-indirect Exciton Condensate Phases in Double Bilayer Graphene

TL;DR

This paper develops a theoretical phase diagram for exciton condensates in double bilayer graphene, revealing diverse phases and control-dependent stability of chiral condensate states.

Contribution

It introduces a comprehensive theory predicting various exciton condensate phases and their electrical control in double bilayer graphene systems.

Findings

Identification of multiple stable exciton condensate states.

Discovery of chirality-dependent stability under electrical control.

Mapping of phase diagram in displacement-field/inter-bilayer-bias space.

Abstract

We present a theory of spatially indirect exciton condensate states in systems composed of a pair of electrically isolated Bernal graphene bilayers. The ground state phase diagram in a two-dimensional displacement-field/inter-bilayer-bias space includes layer-polarized semiconductors, spin-density-wave states, exciton condensates, and states with mixed excitonic and spin order. We find that two different condensate states, distinguished by a chirality index, are stable under different electrical control conditions.