Atomic‐Scale Spin‐Valve Control of Interlayer Excitons in Twisted WSe ₂ /CrSe ₂ /WSe ₂ Heterostructures

Interlayer excitons in transition‐metal dichalcogenide (TMD) van der Waals heterostructures offer long lifetimes, out‐of‐plane dipoles, and valley‐selective optical selection rules. However, active and energy‐efficient control of their formation and recombination remains elusive. Here we demonstrate an interface‐engineering strategy that enables magnetic control of interlayer excitons by inserting a monolayer ferromagnet, CrSe 2 , as an atomic‐scale spin‐valve spacer within a twisted WSe 2 homobilayer. At low temperature, the twisted WSe 2 bilayer supports highly efficient conversion from intralayer to interlayer excitons, providing a sensitive platform to probe interlayer charge transfer. Introducing CrSe 2 suppresses interlayer coupling and produces pronounced thermomagnetic signatures near the Curie temperature (∼65 K), evidencing strong coupling between magnetic fluctuations and exciton dynamics. Under external magnetic fields up to 9 T, the interlayer‐exciton emission is reversibly modulated while intralayer emission is enhanced, consistent with spin‐selective tunnelling that regulates interlayer charge transfer. First‐principles calculations support CrSe 2 ‐mediated spin filtering and reveal stacking‐angle‐dependent charge transfer. These findings establish magnetic spin filtering as an effective strategy for manipulating excitonic states, opening pathways toward spin–exciton hybrid architectures and quantum optoelectronic devices at the atomic scale.