One-Dimensional Brownian Motion on Unpatterned Two-Dimensional Crystal Surfaces

Conventional one-dimensional (1D) Brownian motion on surfaces relies on physical tracks such as prefabricated channels or grooves. Here, we demonstrate through molecular dynamics simulations that a monolayer polymeric C_{60} nanoflake can undergo persistent 1D Brownian motion on unpatterned, atomically flat crystalline surfaces including graphene, hexagonal boron nitride, and molybdenum disulfide. Initially placed at an arbitrary angle, the flake spontaneously rotates into a low-energy stacking configuration with the substrate and then slides along a specific crystallographic axis. This directional behavior stems from a symmetry-broken interfacial potential featuring groovelike energy minima, which act as intrinsic, energetic tracks. Moreover, the sliding direction can be deliberately switched by rotating the nanoflake at predetermined locations, enabling programmable, angstrom-precision transport of adsorbed nanoscale cargos.