Moiré-Pattern Evolution Couples Rotational and Translational Friction at Crystalline Interfaces

The sliding motion of objects is typically governed by their friction with the underlying surface. Compared to translational friction, however, rotational has received much less attention. Here, we experimentally and theoretically study depinning orientational dynamics two-dimensional colloidal crystalline clusters on periodically corrugated surfaces in presence magnetically exerted torques. We demonstrate that traversing locally commensurate areas moir\'e pattern through edges clusters, which hindered potential barriers during cluster rotation, controls its depinning. measured thresholds as a function size strikingly collapse onto universal theoretical curve predicts possibility superlow-static-torque state for large clusters. further reveal cluster-size-independent rotation-translation transition when lattice-matched are driven jointly torque force. Our work provides guidelines design nanomechanical devices involve motions atomic surfaces.