Atomic-Scale Spin-Valve Control of Interlayer Excitons in Twisted WSe₂/CrSe₂/WSe₂ 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, CrSe₂, as an atomic-scale spin-valve spacer within a twisted WSe₂ homobilayer. At low temperature, the twisted WSe₂ bilayer supports highly efficient conversion from intralayer to interlayer excitons, providing a sensitive platform to probe interlayer charge transfer. Introducing CrSe₂ 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 CrSe₂-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.