今天，看了IJMPB的一篇论文，看后写成本博文，供搞超导者想想。

       P W Anderson 最近发表论文：BCS: the scientific “love of my life”. International Journal of Modern Physics B, Vol.24, 3983-3998, 2010

       Abstract: After short comments on my early addenda to BCS — gauge invariance and the Anderson–Higgs mechanism, the dirty superconductor “theorem,” and the spinor representation — I focus on the interaction mechanisms which cause electron–electron pairing. These bifurcate into two almost non-overlapping classes. In order to cause electrons to pair in spite of the strong, repulsive, instantaneous Coulomb vertex, the electrons can evade each others’ propinquity on the same site at the same time either dynamically, by retaining 􀀀0 (s-wave) relative symmetry, but avoiding each other in time— called “dynamic screening” — or by assuming a non-symmetric relative wave function, avoiding each other in space. All simple metals and alloys, including all the (so far) technically useful superconductors, follow the for-mer scheme. But starting with the first discovery of “heavy-electron” super-conductors in 1979, and continuing with the “organics” and the magnetic transition metal compounds such as the cuprates and the iron pnictides, it appears that the second class may turn out to be numerically superior and theoretically more fascinating. The basic interaction in many of these cases appears to be the “kinetic exchange” or superexchange characteristic of magnetic insulators.

文中有一句话：

I will follow a line here that I adumbrated in 2002 in a general talk7 which started out from the incontro-vertible fact that electrons, if brought close enough to each other, experience the strong Coulomb repulsion e2/r, so that if one is to bind them together in pairs one must somehow evade this hard core repulsion.

还有这样一句话：In my experience common sense usually trumps formalism.

文中强调：It seems very likely that they are all based on the second method of avoiding the hard Coulomb core of the electron–electron interaction, and therefore are all cases of unconventional, non-BCS pairing (although of course they are all, at a deeper level, based on the BCS coherent state wave-function.) Therefore an unbiased count of superconductors might well find that this is the majority case. In most of these there is good reason for ignoring the phonon coupling; and the prevalence of nearby magnetic states strongly suggests that the magnetic interaction exemplified by the t-J renormalized Hamiltonian is the major culprit in the pairing.

最后：In summary: The electron–electron interaction which is responsible for turning most metals into superconductors at low enough temperature seems to belong to one or the other of two almost non-overlapping classes. For the simple metals and alloys, the dynamic screening mechanism elaborated from the original BCS phonon scheme is one of the best-attested truths of quantum materials theory. This is responsible for almost all technically useful superconductors, so far. But there is a numerically far larger, if technolog-ically unimportant, category of materials that depend on exotic Pitaevskii-Thouless pairs with complex internal wave functions, vanishing at the origin in order to evade the Coulomb self-interaction U.

我的论文：Xiao Jianhua, Formulating Josephson effects and vortices by reformulated Maxwell equations, International Journal of Modern Physics B, vol.23, issue 20-21, pp 4384-4394, 2009 也谈的是类似问题，但是，谈的是一般性宏观理论。看了P W Anderson论文后，感到很是有自信心，感到自己在研究上有很多的朋友。也表明我的路数是对的。这是值得记录下来的。另外，真为论文：肖建华. 变形分子的电子运动及超导条件, 原子与分子物理学报, Vol.23(增刊), 2006，231-235 在国内被嘲笑而感到国内学术界的。。。。。。