Angle-Resolved Photoemission, Inverse Photoemission, and X-Ray Absorption Studies of Superconductive and Non-Superconductive Bi-Sr-Ca-Y-Cu-O

Abstract

Comparative angle-resolved photoemission (ARPES), angle- resolved inverse photoemission (ARIPES), and angle-resolved x-ray absorption (ARXAS) studies of Br₂Sr₂Ca_1-xY_xCu₂O₈ (x=0.0-0.6) were reported. ARPES and ARXAS results show that hole-doping in an insulator (x=0.6) produces new electronic states in the charge-transfer gap and the density of the new electronic states increases with the hole-concentration. In the “over-doped” region (x=0.0 and 0.2), a slight rigid shift of the bands crossing the Fermi level was observed, suggesting that a rigid-band picture is recovered in the “over-doped” region. ARIPES result confirms that there are two bands which cross the Fermi level centered at the Г point in the Brillouin zone. ARXAS shows that hole-doping causes a transfer of weight of the electronic states from the lowest unoccupied states (upper Hubbard band) to the mid-gap states produced by the hole-doping in the vicinity of the Fermi level.