Department of Physics, University of Kerala, Kariavattom, Thiruvananthapuram-695581, India.
Phys Rev E. 2023 May;107(5-1):054601. doi: 10.1103/PhysRevE.107.054601.
We present the inertial active dynamics of an Ornstein-Uhlenbeck particle in a piecewise sawtooth ratchet potential. Using the Langevin simulation and matrix continued fraction method (MCFM), the particle transport, steady-state diffusion, and coherence in transport are investigated in different parameter regimes of the model. Spatial asymmetry is found to be a key criterion for the possibility of directed transport in the ratchet. The MCFM results for net particle current of overdamped dynamics of the particle agree well with the simulation results. The simulated particle trajectories for the inertial dynamics and the corresponding position and velocity distribution functions reveal that the system passes through an activity-induced transition in the transport from the running phase to the locked phase of the dynamics. This is further corroborated by the mean square displacement (MSD) calculations, where the MSD gets suppressed with increase in the persistent duration of activity or self-propulsion in the medium and finally approaches zero for a very large value of self propulsion time. The nonmonotonic behavior of the particle current and Péclet number with self-propulsion time confirms that the particle transport and its coherence can be enhanced or reduced by fine tuning the persistent duration of activity. Moreover, for intermediate ranges of self-propulsion time as well as mass of the particle, even though the particle current shows a pronounced unusual maximum with mass, there is no enhancement in the Péclet number, instead the Péclet number decreases with mass, confirming the degradation of coherence in transport.
我们展示了奥恩斯坦-乌伦贝克（Ornstein-Uhlenbeck）粒子在分段锯齿形棘轮势中的惯性主动动力学。使用朗之万模拟和矩阵连分式方法（MCFM），研究了在模型的不同参数区域中，粒子输运、稳态扩散和输运中的相干性。发现空间不对称性是实现棘轮定向输运的关键条件。对于粒子的过阻尼动力学的净粒子流，MCFM 结果与模拟结果吻合良好。惯性动力学的模拟粒子轨迹以及相应的位置和速度分布函数表明，系统在动力学的运行相到锁定相的输运中经历了活性诱导的转变。这进一步得到了均方位移（MSD）计算的证实，其中随着活性或自推进在介质中的持续时间的增加，MSD 受到抑制，并且最终对于自推进时间的非常大的值接近零。随着自推进时间的非单调行为，粒子电流和佩克莱数证实了通过精细调整活性的持续时间，可以增强或减少粒子输运及其相干性。此外，对于中等范围的自推进时间以及粒子的质量，即使粒子电流随质量显示出明显的异常最大值，佩克莱数也没有增加，相反，佩克莱数随质量减小，这证实了输运中相干性的退化。
