Evidence of Redistribution of the Itinerant holes Below Tc in Bi2Sr2CaCu2O8 Superconductors: A Polarised X-ray Absorption Study

The microscopic electronic structure of high-quality superconducting Bi2Sr2CaCu2O8+y (Bi2212) single crystals has been investigated in the normal and superconducting states by polarized x-ray-absorption (XAS) measurements. The O K-edge XAS results led us to conclude the presence of a significant density of p(z) symmetry orbitals for itinerant holes. We observed a reproducible increase in the number of O 2p(x,y) itinerant holes accompanied by a decrease of the O K XAS transition in the upper Hubbard band (covalent holes) while going from the normal to the superconducting state of the system. The increase of O 2p,, holes was confirmed by an increase in the 3d(9)L/3d(9) ratio estimated from Cu L(3) XAS measurements. This is in agreement with earlier inverse photoemission measurements and constitutes evidence for the redistribution of the itinerant holes below the transition temperature (T-c)