Highly Nonequilibrium Steady State Induced by a Locally Nonchaotic Energy Barrie

In this research, we investigate the concept of locally nonchaotic energy barrier, e.g., a narrow step in an external force field. The step width is much less than the nominal mean free path of the particles, so that the particle trajectories inside the step tend to be nonchaotic. Our analyses suggest that under the condition of local nonchaoticity, the steady-state particle distribution cannot reach thermodynamic equilibrium. It has interesting effects: When the energy barrier is varied in an isothermal cycle, the produced work at the low-potential shelf is more than the consumed work at the high-potential shelf; when the step forms an asymmetric couple with a wide ramp, at the steady state, the particle velocity distribution may be anisotropic.



We show that although these phenomena seem counterintuitive, they strictly follow the basic principle of maximum entropy. What makes the system unique is that the narrow step interrupts the probability distribution of local microstates, and imposes additional constraints on the global microstates, so that entropy reaches a nonequilibrium maximum.



This finding will have profounds impact on many aspects of statistical mechanics. It may enable high-efficiency heat and mass transfer, high-power energy harvesting, etc.