On the basis of an indirect-exchange pairing mechanism of superconductivity we present a consistent interpretation of doping phenomena in both hole-doped as well as electron-doped high-Tc superconductors. We argue that in all these materials the unifying feature is the existence of a correlated narrow band of electron states formed due to doping. Numerous experimental evidences for the occurrence of such a band (reflectivity, thermoelectric power, electrical resistivity, X-ray absorption, point-contact tunneling etc.) now exist.
Assuming the existence of such a band it was earlier shown that the indirect-exchange (superexchange) coupling between electrons in this band via closed-shell oxygen anions is attractive in the s-wave channel and leads to high-Tc superconductivity. Within the framework of this pairing mechanism, recent doping experiments (for both types of doping) can be given a unified interpretation. In addition, definitive predictions of the doping conditions under which critical temperatures are expected to enhance, are made.
Volume 43, 2020
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