INCREASED DENSITY OF THE INPLANE AND OUT-OF-PLANE DOPING HOLES IN THESUPERCONDUCTING STATE OF HGBA2CA2CU3OY

We have studied the electronic structure near the Cu-O planes in the n ormal and superconducting states in a high-quality HgBa2Ca2Cu3Oy thick film using polarized x-ray absorption in order to get quantitative in formation on the changes in density and symmetry of the itinerant hole s. We have observed, in our analysis of the Cu L-3-edge absorption spe ctra, an increase in the density of doping holes along the planes para llel and perpendicular to the Cu-O sheers while going from the normal to the superconducting state. Our results show that some of the holes have 3d(z)2 symmetry and moreover their density also increases as the system goes to the superconducting state. The results have been discus sed in light of the earlier published results on other cuprate superco nducting systems and a probable local and short-range structural chang e in the CuO5 pyramid which may be associated with the superconducting transition.