Exploring spin multiplicity in MoS2

Abstract

The study of native point-defect-induced spin centres and the synergy of their origin and dynamics are key factors for developing the next-generation spintronics and quantum technologies using quasi-2D transition-metal dichalcogenides (TMDCs). With the help of low-temperature electron paramagnetic resonance (EPR) measurements and first-principles calculations within density functional theory (DFT), herein we report for the very first time the presence of high-spin paramagnetic centres Mo³⁺ and Mo²⁺ in sulfur-deficient hexagonal molybdenum disulfide (2H-MoS_2−x) nanocrystals. This in fact opposes the established notion of spin S = 1/2 mediated by Mo⁵⁺ centres reported so far. The intrinsic lattice strain generated in the nanostructure was found to play a crucial role for such spin localization in this layered material. By performing spin-echo measurements, we find that molybdenum interstitials (S = 3/2) possess the shortest spin–lattice relaxation time (T₁) as compared to the sulfur (S = 3/2) and oxygen vacancies (S = 1/2). Moreover, the temperature-dependent T₁ measurements revealed a direct process for the spin–lattice relaxation of interstitial defects and a Raman process for the vacancy sites.