Surface plasmon polariton-enhanced exciton-mediated magnetic proximity effect in twisted CrOCl/CrOCl/WSe₂ heterostructures

The magnetic proximity effect enables interfacial modulation of excitonic and spin-valley properties in transition metal dichalcogenides (TMDs), offering a versatile route toward next-generation spintronic and valleytronic devices. However, the inherently weak photoluminescence (PL) of bright excitons—suppressed by proximity-induced darkening mechanisms—hinders the optical detection of magnetic interactions. Here, we demonstrate substantial exciton emission enhancement in CrOCl/WSe₂ (HS) and twisted 90°-CrOCl/CrOCl/WSe₂ (THS) heterostructures by employing plasmonic Au nanopillar arrays to activate surface plasmon polariton (SPP) coupling. The neutral exciton emission intensity is enhanced by factors of 5 and 18 for HS/Au and THS/Au, respectively, with enhancements persisting under high magnetic fields and elevated temperatures (~ 10-fold in THS/Au). Enabled by this amplification, we observe pronounced Zeeman splitting and modified intervalley relaxation pathways, indicating significant magnetic proximity interactions. Finite-element simulations and first-principles calculations reveal that the enhancement arises from local electromagnetic field concentration and layer-dependent interfacial coupling. Our results establish SPP-assisted PL enhancement as an effective strategy for probing weak magneto-optical signatures, paving the way for detailed exploration of exciton–magnon coupling and interface-driven quantum phenomena in two-dimensional (2D) magnetic heterostructures.