Spiechowicz Jakub, Łuczka Jerzy
Institute of Physics, University of Silesia, 40-007 Katowice, Poland.
Chaos. 2015 May;25(5):053110. doi: 10.1063/1.4921211.
We study diffusion of the Josephson phase in the asymmetric superconducting quantum interference device (SQUID) subjected to a time-periodic current and pierced by an external magnetic flux. We analyze a relation between phase diffusion and quality of transport characterized by the dc voltage across the SQUID and efficiency of the device. In doing so, we concentrate on the previously reported regime [J. Spiechowicz and J. Łuczka, New J. Phys. 17, 023054 (2015)] for which efficiency of the SQUID attains a global maximum. For long times, the mean-square displacement of the phase is a linear function of time, meaning that diffusion is normal. Its coefficient is small indicating rather regular phase evolution. However, it can be magnified several times by tailoring experimentally accessible parameters like amplitudes of the ac current or external magnetic flux. Finally, we prove that in the deterministic limit this regime is essentially non-chaotic and possesses an unexpected simplicity of attractors.
我们研究了在受到时间周期电流作用且被外部磁通量穿透的非对称超导量子干涉器件（SQUID）中约瑟夫森相位的扩散。我们分析了相位扩散与以SQUID两端直流电压表征的输运质量以及器件效率之间的关系。在此过程中，我们专注于先前报道的一种情况[J. Spiechowicz和J. Łuczka，《新物理学杂志》17，023054（2015）]，在这种情况下SQUID的效率达到全局最大值。长时间来看，相位的均方位移是时间的线性函数，这意味着扩散是正常的。其系数较小，表明相位演化相当规则。然而，通过调整实验可获取的参数，如交流电流的幅度或外部磁通量，它可以被放大几倍。最后，我们证明在确定性极限下，这种情况本质上是非混沌的，并且具有意想不到的吸引子简单性。
