Competing magnetic states in transition metal dichalcogenide moir\'e materials

TL;DR

This paper investigates the magnetic and electronic phases in twisted transition metal dichalcogenide heterobilayers, revealing multiple magnetic states and the prominence of ferromagnetic insulators near the metal-insulator transition.

Contribution

It combines Hartree-Fock calculations with strong-coupling expansions to identify four magnetic and one nonmagnetic state in TMD moiré materials, highlighting ferromagnetic insulators.

Findings

Four magnetic states and one nonmagnetic state identified.

Ferromagnetic insulators are prominently stabilized.

Multiple phase transitions near the metal-insulator boundary.

Abstract

Small-twist-angle transition metal dichalcogenide (TMD) heterobilayers develop isolated flat moir\'e bands that are approximately described by triangular lattice generalized Hubbard models [PhysRevLett.121.026402]. In this article we explore the metallic and insulating states that appear under different control conditions at a density of one-electron per moir\'e period, and the transitions between them. By combining fully self-consistent Hartree-Fock theory calculations with strong-coupling expansions around the atomic limit, we identify four different magnetic states and one nonmagnetic state near the model phase diagram's metal-insulator phase-transition line. Ferromagnetic insulating states, stabilized by non-local direct exchange interactions, are surprisingly prominent.