SU(4) chiral spin liquid, exciton supersolid and electric detection in moir\'e bilayers

TL;DR

This paper explores moiré bilayers as a platform for realizing and detecting exotic quantum phases, including SU(4) spin liquids and exciton supersolids, through electrical measurements and phase tuning.

Contribution

It introduces an SU(4) spin model on triangular lattices in moiré bilayers, predicting novel phases like chiral spin liquids and exciton supersolids, and proposes electrical detection methods.

Findings

Identification of SU(4) symmetric crystallized phase.

Prediction of SU(4)$_1$ chiral spin liquid phase.

Proposal of exciton supersolid phases with inter-layer coherence.

Abstract

We propose moir\'e bilayer as a platform where exotic quantum phases can be stabilized and electrically detected. Moir\'e bilayer consists of two separate moir\'e superlattice layers coupled through the inter-layer Coulomb repulsion. In the small distance limit, an SU(4) spin can be formed by combining layer pseudospin and the real spin. As a concrete example, we study an SU(4) spin model on triangular lattice in the fundamental representation. By tuning a three-site ring exchange term $K\sim \frac{t^3}{U^2}$, we find SU(4) symmetric crystallized phase and an SU(4)$_1$ chiral spin liquid (CSL) at the balanced filling. We also predict two different exciton supersolid phases with inter-layer coherence at imbalanced filling under displacement field. Especially, the system can simulate an SU(2) Bose-Einstein-condensation (BEC) by injecting inter-layer excitons into the magnetically ordered Mott insulator at the layer polarized limit. Smoking gun evidences of these phases can be obtained by measuring the pseudo-spin transport in the counter-flow channel.