Photoemission study of the chemical bond nature of Ba2YCu3OY

Abstract The Chemical bond nature of Ba 2 YCu 3 O y (6 6.4). The peak intensity ratio of the satellite peak to the main peak ofCu2p 3/2 state was always smaller in Ba 2 YCu 3 O y than in CuO. The peak width of the Cu 2p main peak changes from a wider value to a narrower value than that of CuO. This means that the Ba 2 YCu 3 O y compound always contain trivalent or monovalent Cu ions as well as divalent ions. A weak-bonding oxygen peak reduces with y, but still remains even below y=6.2 It suggests the existence of hole in the O2p state of O atoms at the top of pyramid. The two valence states of Ba ion indicates the valence charge fluctuation of Ba atom. These results indicate the possibility of the charge-fluctuation superconducting mechanism.