Modulation of interlayer coupling in bilayer MoS₂ through Li⁺ intercalation

The interlayer coupling of layered two-dimensional (2D) materials plays a crucial role in their physical properties. As an additional degree of freedom of 2D materials, the modulation of interlayer distance has emerged as a prominent research focus. In this work, we modulated the interlayer distance of bilayer MoS₂ by introducing lithium ions (Li⁺) through intercalation, thereby changing the interlayer coupling. Experimental results reveal significant responses in the absorption peaks of both intra- and interlayer excitons following Li⁺ intercalation. Specifically, the energy difference between A and B excitons decreased, and the oscillator strength of interlayer excitons diminished. The deduced interlayer distance expanded from 0.60 to 0.62 nm, confirming the intercalation of Li⁺. The electrical measurements and differential reflectance spectra demonstrated the reversibility of this intercalation process. These findings offer a dedicated strategy for modulating the excitonic states by controlling the interlayer distance in van der Waals (vdW) bilayer systems.