Bogolyubov Institute for Theoretical Physics, 03680 Kyiv, Ukraine.
J Phys Condens Matter. 2010 Apr 21;22(15):155105. doi: 10.1088/0953-8984/22/15/155105. Epub 2010 Mar 9.
We study the dynamics of large polarons in diatomic molecular chains, at zero temperature, under the influence of an external, periodic in time, electric field of zero mean value. We show that in asymmetric chains, i.e. chains with two different atoms per unit cell, a harmonic unbiased field causes a drift of such polarons. Such a drift current, known as the ratchet phenomenon, depends strongly on the parameters of the chain; in particular, on the extent of the anisotropy of the chain and on the size of the polaron. Moreover, the drift takes place only if the intensity and the period of the field exceed some critical values which also depend on the parameters of the chain. We show that this directed current of polarons is a complicated phenomenon. It takes place in dissipative systems with a broken spatial symmetry and is generated by the interplay between the Peierls-Nabarro barrier and the impact of the external field on the charged polarons. The dependence of the amplitude of the polaron oscillations, the size of the drift per period of the external field and the average velocity are determined as a function of the intensity of the field and of its frequency.
我们研究了在零温度下，在零均值的外部时变周期性电场作用下，双原子分子链中大极化子的动力学。我们表明，在不对称链中，即每个单元晶格中有两个不同原子的链中，谐波非偏置场会导致这种极化子的漂移。这种漂移电流，即所谓的棘轮现象，强烈依赖于链的参数；特别是，它取决于链的各向异性程度和极化子的大小。此外，如果场的强度和周期超过某些也取决于链参数的临界值，则会发生漂移。我们表明，这种极化子的定向电流是一种复杂的现象。它发生在具有空间对称性破缺的耗散系统中，是由 Peierls-Nabarro 势垒与外部场对带电极化子的影响之间的相互作用产生的。极化子振动的幅度、每个外场周期的漂移大小和平均速度的依赖关系作为场强度和频率的函数来确定。
