Strain-Dependent Band Splitting and Spin-Flip Dynamics in Monolayer WS<sub>2</sub>.

Yang, Shichao; Chen, Wenwei; Sa, Baisheng; Guo, Zhiyong; Zheng, Jingying; Pei, Jiajie; Zhan, Hongbing · Nano Lett · 2023

basic_science · Level V

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Abstract

Triggered by the expanding demands of semiconductor devices, strain engineering of two-dimensional transition metal dichalcogenides (TMDs) has garnered considerable research interest. Through steady-state measurements, strain has been proved in terms of its modulation of electronic energy bands and optoelectronic properties in TMDs. However, the influence of strain on the spin-orbit coupling as well as its related valley excitonic dynamics remains elusive. Here, we demonstrate the effect of strain on the excitonic dynamics of monolayer WS<sub>2</sub> via steady-state fluorescence and transient absorption spectroscopy. Combined with theoretical calculations, we found that tensile strain can reduce the spin-splitting value of the conduction band and lead to transitions between different exciton states via spin-flip mechanism. Our findings suggest that the spin-flip process is strain-dependent, provides a reference for application of valleytronic devices, where tensile strain is usually existing during their design and fabrication.