Spinon pairing induced by chiral in-plane exchange and the stabilization of odd-spin Chern number spin liquid in twisted ${\rm MoTe}_2$

TL;DR

This paper predicts a novel gapped spin-liquid phase with a quantized spin-Chern number in twisted MoTe$_2$, driven by in-plane spin-exchange interactions, and explores its phase transitions under external electric fields and varying twist angles.

Contribution

It introduces a new mechanism for stabilizing a spin-liquid with a high spin-Chern number via spinon pairing in twisted MoTe$_2$, linking symmetry, topology, and experimental observations.

Findings

Gapped spin-liquid with spin-Chern number three stabilized at small twist angles.

Transition to an anomalous Hall insulator under electric field.

Transition to in-plane antiferromagnet with increasing twist angle.

Abstract

The unusual structure and symmetry of low-energy states in twisted transition metal dichalcogenides leads to large in-plane spin-exchange interactions between spin-valley locked holes. We demonstrate that this exchange interaction can stabilize a gapped spin-liquid phase with a quantized spin-Chern number of three when the twist angle is sufficiently small and the system lies in a Mott insulating phase. The gapped spin liquid may be understood as arising from spinon pairing in the DIII Altland-Zirnbauer symmetry class. Applying an out of plane electric field or increasing the twist angle is shown to drive a transition respectively to an anomalous Hall insulator or an in-plane antiferromagnet. Recent experiments indicate that a spin-Chern number three phase occurs in twisted MoTe$_2$ at small twist angles with a transition to a quantum anomalous Hall phase as the twist angle is increased above a critical value of about $2.5^\circ$ in absence of applied electric field.