Interplay between charge transfer and magnetic proximity effects in WSe2/CrCl3 heterostructures

Abstract

Ferromagnetism in van der Waals systems with diverse spin arrangements opened a pathway to use proximity magnetic fields to activate the properties of materials that would otherwise require external stimuli. Herein, we demonstrate this concept by creating heterostructures comprising a bulk CrCl₃ antiferromagnet with in-plane easy-axis magnetization and a monolayer (ML) WSe₂ semiconductor. Photoluminescence and magnetic force microscopy techniques were performed to reveal the interaction between the relevant layers in the WSe₂/CrCl₃ heterostructures (HSs). The quenching of the WSe₂ emission is apparent in the WSe₂/CrCl₃ HSs due to an efficient charge transfer process enabled by the relative band alignment within the structures. Moreover, we demonstrate that at specific spatial locations in the structures, the magnetic proximity effect between the WSe₂ ML and the CrCl₃ bulk activates dark exciton emission within the WSe₂ ML. The dark exciton emission in the WSe₂ ML survives to a higher temperature than the intraplane Curie temperature (T_C) of the CrCl₃ because of its elevated T_C in the strained regions of the CrCl₃ layer. Our findings are relevant to the development of spintronics and valleytronics with long-lived dark states on technological timescales, as well as to sensing applications of local magnetic fields realized simultaneously in multiple dimensions.