Defect-induced anomalous magnetic response of valley polarization in multilayer-corralled Mo S 2 monolayers

Various strategies have been explored to manipulate the valley degrees of freedom in transition metal dichalcogenides, given their potential applications in quantum information. However, the influence of defects on valley polarization in these materials has received relatively little attention. Here we present findings on the significantly enhanced valley polarization and magnetic response of excitons in $\mathrm{Mo}{\mathrm{S}}₂$ monolayers surrounded by multilayers, achieved through an argon-etched assisted chemical vapor deposition. Low-temperature optical spectroscopy measurements support the identification of sulfur vacancies and their impact on the excitonic properties of the $\mathrm{Mo}{\mathrm{S}}₂$ monolayers. In addition, circular polarization resolved magnetophotoluminescence measurements reveal enhanced valley polarization and the asymmetric magnetic responses of both band-edge free and in-gap bound excitons, which can be attributed to the formation of charged dark excitons. Our study opens avenues for controlling valley polarization and investigating novel quantum optical phenomena through defect engineering in two-dimensional semiconductors.