Topological Phases in AB-Stacked MoTe$_2$/WSe$_2$: $\mathbb{Z}_2$ Topological Insulators, Chern Insulators, and Topological Charge Density Waves

TL;DR

This paper models the quantum phase diagram of AB-stacked MoTe$_2$/WSe$_2$, revealing topological insulators, Chern insulators, and charge density waves driven by electron interactions and external fields.

Contribution

It provides a theoretical framework predicting various topological and magnetic phases in MoTe$_2$/WSe$_2$ based on self-consistent Hartree-Fock calculations.

Findings

Coulomb interactions stabilize a $ ext{Z}_2$ topological insulator at $ u=2$.

Interaction induces multiple competing states at $ u=1$, including spin density waves and ferromagnetism.

Prediction of a topological charge density wave with a honeycomb lattice at $ u=2/3$.

Abstract

We present a theory on the quantum phase diagram of AB-stacked MoTe$_2$/WSe$_2$ using a self-consistent Hartree-Fock calculation performed in the plane-wave basis, motivated by the observation of topological states in this system. At filling factor $\nu=2$ (two holes per moir\'e unit cell), Coulomb interaction can stabilize a $\mathbb{Z}_2$ topological insulator by opening a charge gap. At $\nu=1$, the interaction induces three classes of competing states, spin density wave states, an in-plane ferromagnetic state, and a valley polarized state, which undergo first-order phase transitions tuned by an out-of-plane displacement field. The valley polarized state becomes a Chern insulator for certain displacement fields. Moreover, we predict a topological charge density wave forming a honeycomb lattice with ferromagnetism at $\nu=2/3$. Future directions on this versatile system hosting a rich set of quantum phases are discussed.