A Chemist's View of BCS Theory for Low Tc Superconductivity and Its Relationship to Charge Transfer and High Tc Superconductivity

Abstract

Based on a chemist's understanding of electron transfer, attempts are made to interpret the physicists' BCS theory for low Tc superconductivity in terms of quantum chemical views. To show how to improve and apply some of the principles of the BCS theory for high Tc superconductors, especially those having to do with many-body aspects of correlation, coherence and long-range order, we (1) extend the two-partner, donor-acceptor electron transfer to large periodic systems with cyclic boundary conditions and with double-well potentials beyond Peierls distortion. (2) introduce second-order Jahn-Teller stabilization and introduce vibronic mixing as configuration interaction. To take advantage of existing bonds in high Tc superconductors we propose a linear combination of bonding (two-electron) geminals to form molecular bonding geminals which we call “Vibronic Geminals” after mixing with different running waves of bond structure vibrations. To take advantage of the valence bonds and double-well potentials due to anti-symmetric and other vibrations, we propose a ‘Covalon’ type model for the propagation and tunneling of such bonds which transform as Bosons.