Electronic Structures and Superconducting Mechanism of Ba2Y1Cu3O7

Abstract
The high-T c superconductor Ba2Y1Cu3O7 with the oxygen-deficient perovskite structure was prepared almost in a single-phase with T co of 125 K, T c of 95 and T ce of 93 K. The XPS valence-band spectrum showed a relative large N(E F), density of states at the Fermi level. The XPS Cu 2p3/2 peak is divided into three peaks which are attributed to monovalent, bivalent and trivalent Cu ions with the concentration ratio of 1:2:1. These results and the peculiar lattice structure lead to the T c enhancement mechanism from the plasmon or exciton origin due to the Cu d-hole creation and annihilation resonating with vibration modes of the CuO5 and CuO4 clusters. The T c value was calculated.