Negative differential friction coefficients of two-dimensional commensurate contacts dominated by electronic phase transition

Friction force (f) usually increases with the normal load (N) macroscopically, according to the classic law of Da Vinci—Amontons (f = μN), with a positive and finite friction coefficient (μ). Herein near-zero and negative differential friction (ZNDF) coefficients are discovered in two-dimensional (2D) van der Waals (vdW) magnetic CrI3 commensurate contacts. It is identified that the ferromagnetic—antiferromagnetic phase transition of the interlayer couplings of the bilayer CrI3 can significantly reduce the interfacial sliding energy barriers and thus contribute to ZNDF. Moreover, phase transition between the in-plane (px and py) and out-of-plane (pz) wave-functions dominates the sliding barrier evolutions, which is attributed to the delicate interplays among the interlayer vdW, electrostatic interactions, and the intralayer deformation of the CrI3 layers under external load. The present findings may motivate a new concept of slide-spintronics and are expected to play an instrumental role in design of novel magnetic solid lubricants applied in various spintronic nano-devices.