Intrinsic Friction Diodes at the Interfaces of Two-Dimensional Materials

Friction at homo- and heterogeneous pristine interfaces is conventionally regarded as a symmetric process, with symmetric resistive force in forward and reverse sliding. Here, we reveal an intrinsic nanoscale friction diode effect in common single-crystalline two-dimensional material interfaces through atomistic simulations, including aligned hexagonal boron nitride (h-BN)/h-BN, transition metal dichalcogenide (TMD)/TMD, and graphene/h-BN systems. This counterintuitive phenomenon originates from the asymmetric sliding potential energy surface inherent in specific stacking configurations, resulting in a substantial disparity in friction for opposing sliding directions along the same crystallographic axis. Interestingly, this intrinsic asymmetry can be dramatically amplified by more than an order of magnitude through a dynamic pathway selection mechanism, whereby sliding velocity and temperature determine distinct energetically favorable trajectories. Based on these findings, we establish a general principle for the discovery and design of friction diodes. This work offers fresh insights into directional energy dissipation at the nanoscale and presents effective strategies for designing tunable, directionally responsive tribological systems.