Latent Room-Temperature Tc in Cuprate Superconductors

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The ancient phrase, "All roads lead to Rome" applies to Chemistry and Physics. Both are highly evolved sciences, with their own history, traditions, language, and approaches to problems. Despite all these differences, these two roads generally lead to the same place. For high temperature cuprate superconductors however, the Chemistry and Physics roads do not meet or even come close to each other. In this paper, we analyze the physics and chemistry approaches to the doped electronic structure of cuprates and find the chemistry doped hole (out-of-the-CuO₂-planes) leads to explanations of a vast array of normal state cuprate phenomenology using simple counting arguments. The chemistry picture suggests that phonons are responsible for superconductivity in cuprates. We identify the important phonon modes, and show that the observed Tc 100 K, the Tc-dome as a function of hole doping, the change in Tc as a function of the number of CuO₂ layers per unit cell, the lack of an isotope effect at optimal Tc doping, and the D-wave symmetry of the superconducting Cooper pair wavefunction are all explained by the chemistry picture. Finally, we show that "crowding" the dopants in cuprates leads to a pair wavefunction with S-wave symmetry and Tc≈280-390 K. Hence, we believe there is enormous "latent" Tc remaining in the cuprate class of superconductors.