Anomalous strain dependence of phononic friction between black phosphorus layers

This study reveals unexpected strain-dependent friction, when applied strain to one of two layers of relatively sliding black phosphorus, friction is likely to exhibit characteristic rise and subsequent fall, forming a distinct friction peak. Existence and location of such peak are closely related to magnitude of normal loads. Interfacial pinning is weak at lower normal load, matched dissipation channels are easy to be destroyed, resulting in a monotonic decrease of friction. At higher normal load, tip is also pulled apart once applying a small strain to substrate, stored deformation energy leads to greater energy dissipation than at strain of zero, causing friction to decrease non-monotonically. Moreover, ability of sliding layers to withstand strain decreases with increasing normal loads or temperatures.