The diversity of friction behavior between bi-layer graphenes

For relative sliding between two rigid graphene sheets that are interacted on by a van der Waals force, we show that the friction behavior is significantly dependent on the interlayer separation distance h . Around the equilibrium interlayer distance h e , the friction behavior exactly obeys a linear law. When h is far smaller than h e , the linear friction behavior transforms to over-linear behavior. On the other hand, when h is larger than h e , there is another critical value of the interlayer distance, h c ; when h is larger than h e and smaller than h c , the friction behavior transforms from linear to sub-linear behavior; however, when h is larger than h c , the coefficient of friction becomes negative. Further, the different friction behaviors are found to be well described by a universal power law, τ = μ ∗

Ze Liu

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