Abstract:
The ability to engineer spin-dependent phenomena at the atomic scale is central to next-generation electronic and optoelectronic systems. Two-dimensional (2D) magnet-based van der Waals (vdW) heterostructures provide a unique platform for this purpose by enabling direct control of spin through intrinsic magnetic order and engineered interfacial interactions. In this talk, I will present two representative spin-optoelectronic vdW heterostructures based on Fe₃GeTe₂ and CrI₃. Specifically, we demonstrate that an Fe₃GeTe₂/hexagonal boron nitride ferromagnetic tunneling contact enables efficient spin injection into monolayer WSe₂, where bias-driven spin-polarized hole injection induces a population imbalance between the ±K valleys and results in helicity-dependent electroluminescence. This spin–valley conversion is supported by density functional theory calculations and helicity-resolved electroluminescence measurements. In addition, we demonstrate a spin-polarized light-emitting diode (spin-LED) that operates without an external spin injector. This is achieved using a graphene/h-BN/CrI₃/h-BN/graphene vertical heterostructure, in which monolayer CrI₃ serves as the active light-emitting layer. Although spin-unpolarized carriers are injected through graphene contacts, the electroluminescence becomes circularly polarized due to magnetic-order–governed recombination in CrI₃. Notably, the emission exhibits a polarization degree of ~20%, exceeding most conventional spin-LEDs, and can be reversibly switched with a small magnetic field (~0.17 T). Together, these results point to a unified platform in which 2D magnetic materials enable both spin generation and spin-dependent light emission, opening new opportunities for integrated spin-optoelectronic devices.