场冷Sn-Pb焊料中的涡旋形成与奇异超导态
Vortex formation and exotic superconducting states in field-cooled Sn-Pb solders
AI总结：
本文通过比热和磁化强度研究场冷Sn-Pb焊料，发现其中Sn岛在极高磁通下表现出类第二类超导涡旋态，并揭示升温时磁通驱动力从Sn超导态向Pb超电流转变的机制。
摘要：
涡旋的形成是第二类超导体在磁场（H）下的典型现象。相比之下，第一类超导体由于处于迈斯纳态而不容纳涡旋。作为罕见情况，在第一类超导体的中间态中已观察到涡旋；此外，最近在极低温度（T）和磁场下，在（原本为第一类的）Pb晶体薄膜中观察到具有涡旋的第二类超导性，为研究涡旋物理开辟了新途径。然而，由于缺乏块体实例，原本为第一类元素超导体中这种具有涡旋的类第二类超导态的热力学特性尚未被探测到。在本研究中，我们利用比热和磁化强度研究了相分离Sn-Pb焊料的超导态，以揭示磁通俘获机制。在此，我们表明，当场冷后焊料承载极高磁通时，Sn-Pb焊料中的Sn岛表现出具有涡旋的类第二类超导态。此外，随着T升高，俘获磁通量减少，磁通的驱动力从Sn的第二类超导态转变为包围Sn岛的Pb区域的超电流。场冷Sn-Pb焊料蕴含丰富的块体涡旋形成物理，以及元素（原本为第一类）超导体中异常增强的超电流物理。
英文摘要：
Formation of vortices is a typical phenomenon of type-II superconductors under magnetic fields (H). In contrast, type-I superconductors do not host vortices because of their Meissner state. As rare cases, vortices have been observed in intermediate states of type-I superconductors; in addition, the recent observation of type-II superconductivity with vortices in a (originally type-I) Pb crystal film at extremely low temperature (T) under H has opened new pathway to study vortex physics. However, thermodynamic characteristics of such type-II-like superconducting states with vortices in originally type-I element superconductors have not been detected because of the lack of bulk example. In this study, we investigated superconducting states of phase-separated Sn-Pb solders using specific heat and magnetization to reveal magnetic-flux-trapping mechanisms. Here, we show that Sn islands in the Sn-Pb solders exhibit type-II-like superconducting states with vortices when the solders host extremely high magnetic fluxes after field cooling. Furthermore, with increasing T, the amount of trapped flux decreases, and the driving force of the magnetic flux changes from type-II superconducting states of Sn to supercurrent of Pb regions surrounding the Sn islands. The field-cooled Sn-Pb solders are rich in physics of bulk vortex formation and anomalously enhanced supercurrent in element (originally type-I) superconductors.
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