  Recent AFM experiments have shown that the low-friction sliding of
incommensurate graphite flakes on graphite can be destroyed by torque-induced
rotations. Here we theoretically investigate the stability of superlubric
sliding against rotations of the flake. We find that the occurrence of
superlubric motion critically depends on the physical parameters and on the
experimental conditions: particular scan lines, thermal fluctuations and high
loading forces can destroy the stability of superlubric orbits. We find that
the optimal conditions to achieve superlubric sliding are given by large
flakes, low temperature, and low loads, as well as scanning velocities higher
than those used in AFM experiments.
