Multidimensional sensing of proximity magnetic fields via intrinsic activation of dark excitons in WSe$_2$/CrCl$_3$ heterostructure

TL;DR

This study demonstrates how heterostructures of ferromagnetic CrCl$_3$ and monolayer WSe$_2$ can intrinsically activate dark excitons through proximity magnetic fields, enabling multi-dimensional magnetic sensing without external stimuli.

Contribution

It introduces a novel heterostructure system that intrinsically activates dark excitons via proximity magnetic fields, advancing spintronics and valleytronics applications.

Findings

In-plane proximity fields activate dark excitons in WSe$_2$.

The heterostructure exhibits canted magnetic orientations at 10-30 degrees.

Dark states enable local magnetic field sensing in multiple dimensions.

Abstract

Quantum phenomena at interfaces create functionalities at the level of materials. Ferromagnetism in van der Waals systems with diverse arrangements of spins opened a pathway for utilizing proximity magnetic fields to activate properties of materials which would otherwise require external stimuli. Herewith, we realize this notion via creating heterostructures comprising bulk CrCl$_3$ ferromagnet with in-plane easy-axis magnetization and monolayer WSe$_2$ semiconductor. We demonstrate that the in-plane component of the proximity field activates the dark excitons within WSe$_2$. Zero-external-field emission from the dark states allowed us to establish the in-plane and out-of-plane components of the proximity field via inspection of the emission intensity and Zeeman effect, yielding canted orientations at the degree range of $10^{\circ}$ $-$ $30^{\circ}$ at different locations of the heterostructures, attributed to the features of interfacial topography. Our findings are relevant for the development of spintronics and valleytronics with long-lived dark states in technological timescales and sensing applications of local magnetic fields realized simultaneously in multiple dimensions.