Exchange-bias controlled correlations in magnetically encapsulated twisted van der Waals dichalcogenides

TL;DR

This paper explores how twisted WSe2 bilayers encapsulated with magnetic CrBr3 exhibit tunable correlated states influenced by exchange bias, spin-orbit coupling, and electron interactions, revealing new symmetry-broken phases.

Contribution

It introduces a novel van der Waals heterostructure where exchange bias controls correlated valley and spin states in twisted dichalcogenides.

Findings

Observation of flat bands with tunable valley and spin flavors.

Emergence of spin-ferromagnetic and valley-ferromagnetic states due to interactions.

Control of symmetry-broken states via magnetic alignment.

Abstract

Twisted van der Waals materials have become a paradigmatic platform to realize exotic correlated states of matter. Here, we show that a twisted dichalcogenide bilayer (WSe$_2$) encapsulated between a magnetic van der Waals material (CrBr$_3$) features flat bands with tunable valley and spin flavors. We demonstrate that, when electron-electron interactions are included, spin-ferromagnetic and valley-ferromagnetic states emerge in the flat bands, stemming from the interplay between correlations, intrinsic spin-orbit coupling and exchange proximity effects. We show that the specific symmetry broken state is controlled by the relative alignment of the magnetization of the encapsulation, demonstrating the emergence of correlated states controlled by exchange bias. Our results put forward a new van der Waals heterostructure where symmetry broken states emerge from a genuine interplay between twist engineering, spin-orbit coupling and exchange proximity, providing a powerful starting point to explore exotic collective states of matter.