O K and Cu L_III edge study of itinerant holes in I₂-, HgI₂- and HgBr₂-intercalated BSCCO(2212) single crystals

Intercalation effect on BSCCO (2212) system, although it increases the interlayer distance and the c-axis remarkably, produces only a small change in the transition temperature. Thus, amongst other things, intercalation provides an effective method to investigate the influence of the inter-block coupling. Electrons are transferred from the host Cu-O₂ layers to the guest lmolecules I₂, HgBr₂, HgI₂ leading to evolution of the Tc. For this we have made high resolution XANES study on the O K and Cu L3 edges to estimate the density of the doping holes. We attempt on basis of our and earlier results the evolution of T_c in these as also the much larger decrease produced in T_c for I₂-intercalation for which the increase in basal spacing is the smallest of the three halides.