Soft-x-ray absorption spectroscopy of heterostructured high-T-c superconducting nanohybrids: X-Bi2Sr2CaCu2O8 [X=I, HgI2, and (Py-CH3)(2)HgI4]

Abstract

Unoccupied electronic states of X-Bi2Sr2CaCu2O8 [X-Bi2212, X=1, HgI2, and '(Py-CH3)(2)-HgI4, Py =pyridine] have been probed by O K-edge and Cu L-edge x-ray absorption near-edge structure (XANES) spectra using a bulk-sensitive x-ray-fluorescence-yield technique. In the 0 Is absorption edge of X-Bi2212, the pre-edge feature at similar to 528.3 eV is attributed to transitions into O 2p hole states located in the CuO2 planes. As deduced from 0 K-edge and Cu L-edge x-ray absorption spectra, the hole concentration in the CuO2 planes of X-Bi2212 increases for X=I and HgI2, but decreases for X= (Py-CH3)(2)HgI4, relative to pristine Bi2212. The present XANES results clearly demonstrate that the hole density within the CuO2 planes of intercalated Bi2Sr2CaCu2O8 can be not only decreased but also increased, depending on the chemical character of the intercalants.