Abstract

<sec>Low-dimensional superconductor serves as an excellent platform for investigating emergent superconducting quantum oscillation phenomena. The low-dimensional natures of these materials, originating from the finite size which is comparable with the superconducting coherence length, indicate that the corresponding physical properties will be constrained by quantum confinement effects. Importantly, some of the frontiers and hot issues in low-dimensional superconductors, including the anomalous metal state during the superconductor-insulator transition, spin-triplet pairing mechanism in superconductors, thermal-excited and electrical current-excited vortex dynamics in superconductors, and the “charge-vortex duality” in quantum dot materials and superconducting nanowires, are strongly correlated with the superconducting quantum oscillation effects. In recent years, all the above-mentioned topics have achieved breakthroughs based on the studies of superconducting quantum oscillation effects in low-dimensional superconductors. Generally, the periodicity and amplitude of the oscillation can clearly demonstrate the relation between the geometric structure of superconductors and various superconducting mechanisms. In particular, superconducting quantum oscillation phenomena are always correlated with the quantization of magnetic fluxoids and their dynamics, the pairing mechanism of superconducting electrons, and the excitation and fluctuation of superconducting systems.</sec><sec>In this review article, three types of typical superconducting quantum oscillation effects observed in low-dimensional superconductors will be discussed from the aspects of research methods, theoretical expectations, and experimental results. a) The Little-Parks effect is the superconducting version of the Aharonov-Bohm effect, whose phase, amplitude and period are all helpful in studying superconductivity: the phase reflects the pairing mechanism in superconductors, the amplitude can be used for investigating the anomalous metal state, and the period provides the information about the sample geometry. b) The vortex motion effect is excited by thermal fluctuation or electrical current, and the corresponding oscillation phenomena show distinct temperature-dependent amplitudes compared with the Little-Parks effect. c) The Weber blockade effect originates from the magnetic flux moving across the superconducting nanowire, and such an effect provides a unique nonmonotonic critical current <inline-formula><tex-math id="M1">\begin{document}$ {I}_{\mathrm{C}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20212289_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20212289_M1.png"/></alternatives></inline-formula> under a magnetic field in <inline-formula><tex-math id="M2">\begin{document}$I\text{-}V$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20212289_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20212289_M2.png"/></alternatives></inline-formula> characteristics. The prospects of the above-mentioned quantum oscillation effects of low-dimensional superconductors for applications are also discussed at the end of this review, including quantum computing, device physics and low-temperature physics.</sec>

Highlights

  • Analysis of LP oscillation for the α -BiPd superconducting ring[75]: (a) LP effect where the maximum resistance corresponds to the zero magnetic flux

  • The porous structure is obtained by ionic etching of relations for 4 typical states: SC, AM1, TS and INS. (c)–(e) The oscillation signals in the R-H relations observed from normalized electrical conductance for the superconducting state (c), anomalous metal state (d), and insulating state (e)

  • Magnetoresistance oscillation phenomena originating from the current-induced vortex motion effect[50]: (a) Schematic diagram of the superconducting Nb device structure. (b) The R-T relation of Nb device

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Summary

K c=4 K

下文将分别介绍该方向的几类典型工作, 包 括: 1) 自旋三重态配对的超导体 β -Bi2Pd、自旋三 重态与自旋单态混合配对超导体 α-BiPd 中的利特 尔-帕克斯振荡效应; 2) 手性多壁 WS2 纳米管中的 利特尔-帕克斯效应; 3) 利用利特尔-帕克斯效应研 究高温超导体钇钡铜氧 (YBa2Cu3O7–x, YBCO) 的 超导-绝缘体相变过程中的反常金属态等. 为了直观反映自旋三态配对的 β -Bi2Pd 超导 体与以 Nb 为代表的常规 BCS 超导体之间的差异, Chien 课题组对比了两种材料的利特尔-帕克斯效 应, 如图 3 所示 [66]. 实验结果表明, Nb 磁电阻信号的 利特尔-帕克斯振荡曲线 (图 3(c)) 与常规超导体的 振荡行为 (图 3(a)) 很好地相符, 而多晶 β -Bi2Pd 的利特尔-帕克斯振荡结果 (图 3(d)) 却明显与自旋 三态超导体的振荡特征 (图 3(b)) 相吻合. 在前文对自旋三重态配对超导体的利特尔-帕 克斯效应研究基础上, 约翰斯·霍普金斯大学的 Chien 课题组 [75] 进一步设计实验, 希望通过利特 尔-帕克斯效应证实一些特殊超导体中自旋单态与 自旋三重态配对机制共存的现象. 进一步地, Chien 课题组利用电子束刻蚀技术将样品制成亚微米尺 度的方形超导环, 并在不同温度的磁电阻信号之中 都观察到了极大值位于 Φ′ = (n + 1/2) Φ0 的半整数 利 特 尔 -帕克斯效应 (图 4(a)), 该信号与磁场的 扫描方向无关, 并在其他尺寸的器件中都能够被 观察到, 证实了 α-BiPd 中自旋三重态配对机制 的存在. Analysis of LP oscillation for the α -BiPd superconducting ring[75]: (a) LP effect where the maximum resistance corresponds to the zero magnetic flux. (b) LP effect where the minimum of resistance corresponds to zero magnetic flux. 实验关系的外推曲线相吻合, 说明了实验规律的可 靠性. 最后, 研究者们还通过进一步的分析排除了 钾离子掺杂浓度和管壁厚度两个因素对 TC 的影响, 说明了在该实验条件下 TC 只受到管径这一个变量 的影响 [47]. 然而, 此前基于电声耦合超导机制的理 论分析给出了与实验完全相反的预测 [83], 这说明 目前对纳米管中电声散射机制的理解仍然不够明 晰. 总之, 上述实验结果以对利特尔-帕克斯效应的 分析为桥梁, 为研究超导纳米管中存在的物理机制 提供了重要的实验基础

71 K 75 K 79 K
E Magnetic field
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