Kinetic-energy-dependent over-barrier behaviors of nanorotors in tilted periodic potentials

Thermal-induced transitions between multistable states hold significant interest in stochastic thermodynamics and dynamical control with nanomechanical systems. Here, we study kinetic-energy-dependent over-barrier behaviors in the rotational degree of freedom of silica nanodumbells in tilted periodic potentials. In the rotational degree of freedom, nanodumbbells can undergo critical transitions between librations and rotations as the ellipticity of the trapping laser field changes. These transitions exhibit hysteresis effects, which can be monitored in real time by introducing an additional laterally scattered light. Our experiments elucidate that the distribution of kinetic energy of nanorotors influences the critical transition ellipticities for activating or inhibiting over-barrier behaviors, which is supported by theoretical and numerical analysis. This work lays the groundwork for exploring mesoscopic thermodynamics associated with a broad spectrum of stochastic processes, e.g., non-Markovian thermal noise and evolutions of nonequilibrium steady states.