Anharmonic apical oxygen vibration in high-Tc superconductors

Using time-independent perturbation theory, a theoretical calculation has been performed for the transition temperatures for various high-Tc oxide compounds. It has been assumed that, three electrons are responsible for the superconducting current. Whereas two of these electrons form an exotic bound pair, the third electron causes perturbation H' = βx3 + γx4 with respect to apical oxygen vibrations. From the calculations, the transition temperatures are found to be realistic and comparable with experimental results. (author)