Modulating spin-valley relaxation in WSe₂ with variable thickness VOPc layers

Combining the synthetic tunability of molecular compounds with the optical selection rules of transition metal dichalcogenides (TMDCs) that derive from spin-valley coupling could provide interesting opportunities for the readout of quantum information. However, little is known about the electronic and spin interactions at such interfaces and the influence on spin-valley relaxation. Here, in this work, vanadyl phthalocyanine (VOPc) molecular layers are thermally evaporated on WSe₂ to explore the effect of molecular layer thickness on excited-state spin-valley polarization. The thinnest molecular layer supports an interfacial state which destroys the spin-valley polarization almost instantaneously, whereas a thicker molecular layer results in longer-lived spin-valley polarization than the WSe₂ monolayer alone. The mechanism appears to involve a tightly bound species at the molecule/TMDC interface that strengthens exchange interactions and is largely avoided in thicker VOPc layers that isolate electrons from WSe₂ holes.. Authors: Lubert-Perquel, Daphné [National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000209854307); Cho, Byeong Wook [Sungkyunkwan Univ., Suwon (Republic of Korea)] (ORCID:0009000558942994); Phillips, Alan J. [National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000275294379); Lee, Young Hee [Sungkyunkwan Univ., Suwon (Republic of Korea)] (ORCID:0000000242646083); Blackburn, Jeffrey L. [National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000292375891). DOE Contract: AC36-08GO28308. Subjects: 2D materials; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS,INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; exciton; quantum sensing; spectroscopy; spin