Electron-phonon driven superconductivity: do we really have a microscopic understanding of it?

在元素水星中发现超导电性100年后，我们已经有了无数的超导材料家族，每一种超导材料似乎彼此几乎没有什么共同之处。超导现象完全是关于电荷的运动，就连我们对这种非凡状态的物质机制的理解，至少对所谓的传统超导体来说，也是关于通过电荷波动进行配对的。相比之下，对于较新的超导体，目前关于其机制的许多想法都围绕着“自旋涨落”这一“配对胶”展开。 但为了理解电子如何既能携带电流又能提供配对机制，我们建议回到过去，更深入地了解电子在传统机制中是如何配对的。历史理论(Eliashberg)解释了电子发生了什么，但从来没有同时解释过声子与电子相互作用时发生了什么。在这个意义上，它仍然是一种现象学，我们建议通过先进的理论技术来提供对超导状态的真正微观描述。 这样，我们不仅可以深入了解传统超导体的工作原理，还可以更好地处理一个更困难的问题，即理解一个非传统超导体，因为载流子和配对胶水似乎来自同一个电子。其目标是加深对超导机理的理解，这将有助于材料科学家寻找更高温度的超导。

100 years after the discovery of superconductivity in elemental Mercury, we have innumerable families of superconducting materials, each of which seems to have little in common with one another. The phenomenon of superconductivity is all about the movement of charge, and even our understanding of the mechanism for this remarkable state of matter, at least for so-called conventional superconductors, is about pairing through charge fluctuations. In contrast, for newer superconductors, many of the current ideas about the mechanism involved center around `spin fluctuations' as the `pairing glue'. But to understand how electrons can both carry the current and provide the pairing mechanism, we propose to go back and gain a deeper understanding of how electrons pair in the conventional mechanism. The historical theory (Eliashberg) explains what happens to the electrons, but never really explains simultaneously what happens to the phonons, as they interact with the electrons. In this sense it remains a phenomenology, and we propose to provide a truly microscopic description of the superconducting state, through advanced theoretical techniques. In this way, not only will we gain insights into how the conventional superconductor works, but we should be better equipped to deal with the more difficult problem of understanding an unconventional superconductor where the carriers and the pairing glue appear to originate from the same electrons. The goal is that a deeper understanding of the mechanism of superconductivity will aid material scientists in the search for higher temperature superconductivity.