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arXiv 1408.4607cond-mat.supr-concond-mat.stat-mech
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约瑟夫森结棘轮:有限电容效应

Josephson junction ratchet: effects of finite capacitances

Jakub Spiechowicz, Peter Hänggi, Jerzy Łuczka

摘要:

本文研究了非对称SQUID中的输运,该SQUID由三个电容并联的约瑟夫森结组成,其中两个串联在一个臂上,另一个串联在另一个臂上,外加磁通量,系统同时受到时间周期和恒定电流的作用。我们制定的确定性,以及,SQUID的随机动力学的Stewart-McCumber模型的条款,并推导出一个方程的相位差在一个手臂,其中有效的周期电位是棘轮型,即其反射对称性被打破。在这样做时,我们扩展和推广Zapata等人的早期研究。77,2292(1996)],并在宽参数范围内分析定向输运:覆盖过阻尼到中等阻尼范围,直到其完全欠阻尼范围。因此,我们检测到有趣的功能的负(差分)电导,重复的电压反转,噪声引起的电压反转和热噪声引起的棘轮电流。我们确定了一组参数的棘轮效应是最明显的,并显示如何可以通过定制的外部磁通量控制的方向的运输。

英文摘要:

We study transport in an asymmetric SQUID which is composed of a loop with three capacitively and resistively shunted Josephson junctions: two in series in one arm and the remaining one in the other arm. The loop is threaded by an external magnetic flux and the system is subjected to both a time-periodic and a constant current. We formulate the deterministic and, as well, the stochastic dynamics of the SQUID in terms of the Stewart-McCumber model and derive an equation for the phase difference across one arm, in which an effective periodic potential is of the ratchet type, i.e. its reflection symmetry is broken. In doing so, we extend and generalize earlier study by Zapata et al. [Phys. Rev. Lett. 77, 2292 (1996)] and analyze directed transport in wide parameter regimes: covering the over-damped to moderate damping regime up to its fully under-damped regime. As a result we detect the intriguing features of a negative (differential) conductance, repeated voltage reversals, noise induced voltage reversals and solely thermal noise-induced ratchet currents. We identify a set of parameters for which the ratchet effect is most pronounced and show how the direction of transport can be controlled by tailoring the external magnetic flux.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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