Friction-induced ultrafast charge transfer in van der Waals heterostructures

van der Waals heterostructures stacked by transition metal dichalcogenides and graphene provide a new opportunity for exploring superlubricity. However, the further reduction of friction is limited by the unavoidable charge transfer in the heterostructures. The dynamics of charge transfer occur at picosecond time scale, which cannot be detected by traditional friction instruments, making the friction mechanism of charge transfer unclear. Here, we investigate friction-induced charge transfer in WS₂/graphene heterostructures with ultrafast friction energy dissipation detecting technique. The observed friction exhibits a strong linear relationship with the dissipation rate of interlayer charge transfer. By modulating the band structure of heterostructures, the dissipation rate of interlayer charge transfer can be efficiently tuned from 0.72 to 0.17 ps⁻¹, resulting in a ~ 35% reduction in friction. This work gives the direct explanation of friction-induced charge transfer, which enables the high-performance micro-electro-mechanical systems and new insight into the origin of friction from the perspective of ultrafast electron dynamics.