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arXiv 1004.4533cond-mat.supr-concond-mat.str-el
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d波超导体环和结中的磁通周期性

Flux periodicities in loops and junctions with d-wave superconductors

Florian Loder, Arno P. Kampf, Thilo Kopp

摘要:

本文评述了超导回路中的磁通量周期性。而磁通量的量子化与hc/2 e盛行在足够厚的回路与电流自由的内部,在狭窄的回路的超电流是hc/2 e或hc/e周期与外部磁通量。周期性取决于凝聚态的性质,特别是能谱的多普勒频移。对于直径大于相干长度的环中的s波超导体,相对于能隙的多普勒频移很小,且其热力学性质的hc/2 e周期行为保持不变.然而,对于更小的s波环,更突出的是,任何直径R的窄d波环,多普勒频移对超导载流状态有很强的影响;因此,基本通量周期性实际上是hc/e。它示出解析和数值计算的hc/e的周期分量的超导衰减仅代数为1/R的大d波回路。对于节状超导体,在计算多普勒频移时,必须考虑费米能附近本征的离散性质。此外,我们还研究了多普勒频移是否改变了通过d波超导体的约瑟夫森结的超导电流。对于透明结,约瑟夫森电流的行为类似于回路中的持续超电流。如果用序参量的相位变化除以4 π来确定以hc/e为单位的磁通量,则可以比较这些不同的物理现象。

英文摘要:

The magnetic flux periodicity in superconducting loops is reviewed. Whereas quantization of the magnetic flux with hc/2e prevails in sufficiently thick loops with current free interior, the supercurrent in narrow loops is either hc/2e or hc/e periodic with the external magnetic flux. The periodicity depends on the properties of the condensate state, in particular on the Doppler shift of the energy spectrum. For an s-wave superconductor in a loop with diameter larger than the coherence length, the Doppler shift is small with respect to the energy gap, and the hc/2e periodic behavior of its flux dependent thermodynamic properties is maintained. However, for smaller s-wave loops and, more prominently, narrow d-wave loops of any diameter R, the Doppler shift has a strong effect on the supercurrent carrying state; as a consequence, the fundamental flux periodicity is in fact hc/e. It is shown analytically and numerically that the hc/e periodic component in the supercurrent decays only algebraically as 1/R for large d-wave loops. For nodal superconductors the discrete nature of the eigenergies close to the Fermi energy has to be respected in the evaluation of the Doppler shift. Furthermore, we investigate, whether the Doppler shift modifies the supercurrent through Josephson junctions with d-wave superconductors. For transparent junctions, the Josephson current behaves similar to the persistent supercurrent in a loop. These distinct physical phenomena can be compared, if the magnetic flux in units of hc/e is identified with the phase variation of the order parameter divided by 4 pi.

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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