Ultra-low friction at the interfaces of heterostructures composed of phosphorene and arsenene.

Current research in the field of solid lubrication mainly focuses on graphene, MoS2, and h-BN, highlighting the necessity of exploring the lubricating properties of emerging two-dimensional (2D) materials. Phosphorene and arsenene, as novel 2D materials with puckered structures, exhibit unique anisotropic electronic and mechanical properties. By performing first-principles calculations, we investigated the friction properties at the interfaces of phosphorene/phosphorene and arsenene/arsenene, as well as six heterostructures formed by phosphorene or arsenene with graphene, h-BN, and MoS2. The homojunctions display strong frictional anisotropy, with large differences in sliding barriers among different sliding directions. The heterostructures exhibit significantly lower potential energy corrugations, lower shear strengths, and weaker direction dependence because of the incommensurate contact. Specifically, graphene/phosphorene and graphene/arsenene show structural superlubricity with friction coefficients below 10-3 under a wide range of normal loads (0-10 nN). It is found that the friction behavior is closely dictated by charge redistribution at the interface. The charge redistribution at the interface of graphene/phosphorene is relatively uniform. Conversely, the charge redistribution is highly localized around specific atoms but minimal in other regions at the interface of graphene/arsenene. Notably, the net interlayer charge transfer of the two heterostructures barely changes during sliding. This study provides two promising candidates as solid lubricants, and comprehensive understanding of the friction at the interfaces of phosphorene and arsenene.