Stoner instabilities and Ising excitonic states in twisted transition metal dichalcogenides

TL;DR

This paper reports the discovery of new correlated electronic phases in twisted WSe2, including an antiferromagnetic metal and an Ising excitonic insulator, observed away from lattice commensurability through magnetotransport measurements.

Contribution

It demonstrates the existence of correlated phases outside of rational fillings, revealing new magnetic and excitonic states in twisted TMD systems.

Findings

Identification of an antiferromagnetic metal near the van Hove singularity

Observation of a re-entrant magnetic field-driven insulator

Evidence for an Ising excitonic insulator with balanced electron-hole densities

Abstract

Moir\'e transition metal dichalcogenide (TMD) systems provide a tunable platform for studying electron-correlation driven quantum phases. Such phases have so far been found at rational fillings of the moir\'e superlattice, and it is believed that lattice commensurability plays a key role in their stability. In this work, we show via magnetotransport measurements on twisted WSe2 that new correlated electronic phases can exist away from commensurability. The first phase is an antiferromagnetic metal that is driven by proximity to the van Hove singularity. The second is a re-entrant magnetic field-driven insulator. This insulator is formed from a small and equal density of electrons and holes with opposite spin projections - an Ising excitonic insulator.