Light and warm superconductors: fact or fiction?

BCS theory predicts that light elements should make high temperature superconductors, and that is the consensus in the physics community. Accordingly, NSF and other funding agencies are devoting important resources to such research [1]. Hydrides under high pressure are expected to be high T_c superconductors, and during the last 7 years 15 different such hydrides, e.g. H₃S, LaH₁₀, CSH, etc, have been claimed to be superconductors with T_c's exceeding those of the high T_c cuprates, up to and above room temperature. Many more hydrides have been claimed to be high T_c superconductors based on theoretical evidence, and many other light-element compounds have been predicted to be high T_csuperconductors by analogy with MgB₂. I will argue that NONE of those claims and predictions have been independently and reproducibly verified, and that in fact to date the experimental evidence that light elements favor high temperature superconductivity is ZERO. If what I am arguing is true, it indicates that there is a.fundamental flaw in the BCS assumption that the electron-phonon interaction causes superconductivity. Instead, the theory of hole superconductivity [2] predicts that high temperature superconductivity results from holes conducting through closely spaced negatively charged anions, as is the case in the cuprates, pnictides, and MgB₂, and that the ionic mass is irrelevant.

 

[1] NSF Funding Opportunity - Light and Warm Superconductors, January 27, 2021.

[2] References in https://jorge.physics.ucsd.edu/hole.html.