‘Conventional’ superconductivity, as used in this review, refers to electron–phonon-coupled superconducting electron pairs described by BCS theory. Unconventional superconductivity refers to superconductors where the Cooper pairs are not bound together by phonon exchange but instead by exchange of some other kind, e.g. spin fluctuations in a superconductor with magnetic order either coexistent or nearby in the phase diagram. Such unconventional superconductivity has been known experimentally since heavy fermion CeCu2Si2, with its strongly correlated 4f electrons, was discovered to superconduct below 0.6 K in 1979. Since the discovery of unconventional superconductivity in the layered cuprates in 1986, the study of these materials saw Tc jump to 164 K by 1994. Further progress in high-temperature superconductivity would be aided by understanding the cause of such unconventional pairing. This review compares the fundamental properties of 9 unconventional superconducting classes of materials – from 4f-electron heavy fermions to organic superconductors to classes where only three known members exist to the cuprates with over 200 examples – with the hope that common features will emerge to help theory explain (and predict!) these phenomena. In addition, three new emerging classes of superconductors (topological, interfacial – e.g. FeSe on SrTiO3, and H2S under high pressure) are briefly covered, even though their ‘conventionality’ is not yet fully determined.

中文翻译：

---

非常规超导

本综述中使用的“常规”超导是指 BCS 理论描述的电子-声子耦合超导电子对。非常规超导性是指其中库珀对不是通过声子交换而是通过某种其他类型的交换结合在一起的超导体，例如超导体中的自旋涨落在相图中具有共存或附近的磁序。自从 1979 年发现具有强相关 4f 电子的重费米子 CeCu2Si2 在低于 0.6 K 的温度下超导以来，这种非常规超导性就在实验中得到了证实。 自从 1986 年在层状铜酸盐中发现非常规超导性以来，对这些材料的研究见证了 Tc 跃迁到 1994 年达到 164 K。了解这种非常规配对的原因将有助于在高温超导方面取得进一步进展。这篇综述比较了 9 种非常规超导材料的基本特性——从 4f 电子重费米子到有机超导体，再到只有三个已知成员的类，再到铜酸盐，有 200 多个例子——希望能出现共同的特征来帮助理论解释（并预测！）这些现象。此外，还简要介绍了三类新兴的超导体（拓扑、界面——例如 SrTiO3 上的 FeSe 和高压下的 H2S），尽管它们的“常规”尚未完全确定。这篇综述比较了 9 种非常规超导材料的基本特性——从 4f 电子重费米子到有机超导体，再到只有三个已知成员的类，再到铜酸盐，提供了 200 多个例子——希望能出现共同的特征来帮助理论解释（并预测！）这些现象。此外，还简要介绍了三类新兴的超导体（拓扑、界面——例如 SrTiO3 上的 FeSe 和高压下的 H2S），尽管它们的“常规”尚未完全确定。这篇综述比较了 9 种非常规超导材料的基本特性——从 4f 电子重费米子到有机超导体，再到只有三个已知成员的类，再到铜酸盐，有 200 多个例子——希望能出现共同的特征来帮助理论解释（并预测！）这些现象。此外，还简要介绍了三类新兴的超导体（拓扑、界面——例如 SrTiO3 上的 FeSe 和高压下的 H2S），尽管它们的“常规”尚未完全确定。