High Tc Superconductivity and S-I Transition in Ba–Y–Cu–O

Abstract

Superconductor-Insulator transition and superconductivity have been studied by the measurements of resistivity, specific heat, XPS, a.c.magnetic susceptibility and X-ray diffraction in Ba–Y–Cu–O system. The experimental results show that the S-I (superconductor-insulator) transition which might be driven by the electrons occurs near x=0 and the high electronic density of states at Fermi level usually associated with the high Tc in this system. A λ-type phase transition which is probably related to the antiferromagnetism was also observed near 12K.