Van Hove Singularity-Driven Topological Magnetism in Twisted MoTe2

TL;DR

This paper demonstrates how Van Hove singularities in twisted MoTe2 induce topological magnetism, leading to correlated magnetic states and topological phase transitions tunable via electrostatic doping and magnetic fields.

Contribution

It reveals a novel interplay between Van Hove singularities, strong correlations, and valley topology in twisted MoTe2, resulting in emergent topological magnetic phases.

Findings

Electrostatic tuning to a Van Hove singularity induces anomalous Hall effects.

Identification of a correlated intervalley-coherent antiferromagnetic state.

Observation of a topological Hall effect and transition to a Chern insulator.

Abstract

Van Hove singularities (vHSs) strongly amplify electron interactions and can stabilize correlated phases in topological bands. Here we report signatures of topological magnetism in large-angle twisted bilayer MoTe2 driven by the interplay of vHSs, strong correlations, and valley topology. In a 4.8 degree device, electrostatic tuning to a vHS produces a spontaneous anomalous Hall hot spot near nu = -1. Combined transport and reflective magnetic circular dichroism measurements indicate that this regime is not governed by magnetization alone, but instead emerges from a correlated intervalley-coherent antiferromagnetic state that evolves with doping into a canted phase. With increasing magnetic field, the Hall response develops an additional finite-field component consistent with a topological Hall effect from a noncoplanar spin texture, before transitioning into a C = -1 Chern insulator. Our results establish tunable vHSs in moire topological bands as a route to chiral magnetism and engineering topological phase transitions.