ANOMALIES IN THE ISOTOPE EFFECT IN HIGH-TC SUPERCONDUCTORS - EVIDENCE OF A PLASMON MECHANISM FOR SUPERCONDUCTIVITY

Previous research has revealed that the exponent of the oxygen isotope shift decreases with increasing superconducting transition temperature T(c) in the layered cuprate metal oxides. It is shown in the present paper that this decrease can be explained by a plasmon mechanism for superconductivity. This mechanism involves a Cooper pairing of light current carriers in a wide 2D band. The pairing results from the exchange of virtual quanta of low-frequency collective excitations of the charge density of heavy carriers in a narrow 2D band. These virtual quanta are acoustic plasmons, which hybridize with oxygen vibrational modes.