Effect of isotopic substitution of copper on the critical temperature of the superconducting ceramic Y1Ba2Cu3O7
Vasil'ev B. V. , Lushchikov V. I., Sikolenko V. V.
Electrical measurements reveal no effect of a substitution of the isotopes 63 Cu and 65Cu on the critical temperature of the high-temperature superconductor Y1Ba2Cu307. The absence of an isotopic effect involving copper, along with the absence of such an effect involving the other elements, is interpreted as evidence in favor of a nonphonon mechanism for the high-temperature superconductivity.