Spin-Dependent Excitonic States in Twisted Bilayer WSe₂/Fe₅GeTe₂ Heterostructure

Twisted bilayer transition metal dichalcogenides (TMDs) have generated diverse unusual electrical and optical phenomena and can provide a powerful platform for designing nanodevices with tunable interlayer interaction. Striving to explore novel excitons with spin response in these semiconductor systems is highly desirable, as they highlight the possibility to access complex electronic band structure and magneto-exciton effect, thereby facilitating efficient spin-based information storage via exciton degrees of freedom. Here, fabrication of bilayer WSe₂/Fe₅GeTe₂ (FGT) heterostructures with different stacking phases is reported, and a new hybridized excitonic state T* is defined in both 3R and 2H bilayer WSe₂, which exhibits strong correlations dependent on the FGT spin order. This spin-dependent hybridized exciton is demonstrated to originate from the coupling between injected spin-polarized electrons and neutral excitons, because of the spin-cross-polarized band that obstructs the normal electron-hole annihilation process. Besides, the difference in the coupling strength of the T* exciton attributed to the distinct stacking symmetries in twisted bilayer WSe₂ is further unveiled. These findings open an accessible avenue for designing tailored excitonic states in twisted bilayers, thus offering prospects for the future applications of stacking-engineered opto-spintronics at the integration level.