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arXiv 2411.02011cond-mat.supr-con
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非常规超导体结的全计数统计

Full counting statistics for unconventional superconductor junctions

Tim Kokkeler, Alexander Golubov, F. Sebastian Bergeret, Yukio Tanaka

AI总结:

该研究针对不同类型非常规超导体/正常金属结构建全计数统计理论,纳入热噪声对微分法诺因子的影响,揭示表面安德列夫束缚态特性与结类型对输运噪声的调控规律,为识别超导体配对对称性提供新方法。

摘要:

噪声和电流测量是研究介观系统的核心工具,能揭示电导之外的深层信息。例如,噪声测量表明常规超导体中的输运载流子电荷为2e。噪声功率还取决于结的类型,可区分不同的输运过程。现有理论主要聚焦于常规超导体隧道结中的零温度散粒噪声,这类结中的输运由准粒子和库珀对(Cooper pairs)承载。本文中,我们针对不同类型的非常规超导体/正常金属结建立了全计数统计理论,纳入了热噪声对微分法诺因子(即微分噪声功率与电导的比值)的影响。这类结中存在第三种输运载流子:表面安德列夫束缚态(surface Andreev bound states)。研究发现,具有无色散表面安德列夫束缚态的结在有限温度下表现出负微分法诺因子。相比之下,当存在色散型表面安德列夫束缚态时,噪声功率始终随电压增大而升高,但在对应表面安德列夫束缚态能谱极值的电压处,微分噪声会出现局部极小值。对于正常金属和常规超导体,所有类型的结(包括隧道结和扩散势垒)的微分法诺因子的电压依赖特性均相似。然而,非常规超导体则表现出显著差异,这使得不同类型的结成为识别配对对称性的有效工具。我们的研究结果还凸显了在潜在非常规超导体的噪声功率测量中考虑有限温度效应的重要性,为确定拓扑超导体的配对对称性提供了新途径。

英文摘要:

Noise and current measurements are key tools for studying mesoscopic systems, revealing insights beyond conductance alone. For instance, noise measurements show that transport carriers in conventional superconductors have charge 2e. The noise power also depends on junction type, distinguishing different transport processes. Existing theories focus primarily on zero temperature shot noise in tunnel junctions with conventional superconductors, where transport is carried by quasiparticles and Cooper pairs. Here we develop a full counting statistics theory for unconventional superconductor / normal metal junctions of different types, incorporating the effect of thermal noise on the differential Fano factor, the ratio of differential noise power and conductance. In these junctions there is a third type of transport carrier, surface Andreev bound states. Our study reveals that junctions with dispersionless surface Andreev bound states exhibit negative differential Fano factor at finite temperatures. In contrast, in the presence of dispersive surface Andreev bound states, the noise power always increases with voltage, but there are local minima in the differential noise at those voltages corresponding to the extrema of the surface Andreev bound state spectrum. For normal metals and conventional superconductors the voltage dependence of the differential Fano factor is similar in all types of junctions, including tunnel junctions and diffusive barriers. However, significant differences arise with unconventional superconductors, making distinct junction types valuable tools for identifying pairing symmetries. Our results also highlight the importance of finite temperature effects in noise power measurements for potential unconventional superconductors, offering new means to determine pairing symmetries in topological superconductors.

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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