Polarized XANES Studies of Cu L₃ Edges of Bi‐2212 Superconducting Single Crystals Using Total and Fluorescence Yield Techniques

Abstract

XANES with polarized synchrotron light is now established to be one of the important techniques for the study of the electronic structure of high-T, superconductors in order to find out the symmetry of holes and their implication to the theoretical models proposed to explain superconductivity in these cuprates. The XANES spectra are measured by two methods in the soft X-ray region, namely, total yield (TY) and fluorescence yield (FY) methods, which give different results with respect to out-of-plane Cu 3d(z2) symmetric holes. The reason of this discrepancy is not quite clear. Polarized XANES measurements on Bi-2212 single crystals at the Cu L, edge by the TY and FY methods are reported and the results are discussed in detail.

Polarized x-ray absorption spectroscopy study of the symmetry of unoccupied electronic states near the Fermi level in the system

“…Later reports using the bulk-sensitive 0953-8984/96/142467+11$19.50 c 1996 IOP Publishing Ltd 2467 fluorescence yield (FY) mode [12] showed an almost insignificant intensity for the out-ofplane Cu 3d z 2 states. A recent report by Venkatesh et al [21] lists the probable reasons for the observed discrepancies in the TY and FY data. Still no satisfactory explanation has been given so far regarding the various contradictory observations reported.…”

Simultaneous measurement of XANES in halide-intercalated BSCCO(2212) using electron and fluorescence yield to compare their performance

“…This served to show that the difference in the spectra from the two techniques perhaps mainly arises from the condition of the surface. An earlier report by S. Venkatesh et al(1995) wherein they report a larger intensity the for the Cu L III edge in the FY mode compared to that from the TY mode from a crystal not cleaved in situ also tends to confirm this. Pellegrin et al(1993) have indicated how an alignment error of up to +5% may also contribute to the discrepancies in the measured intensities.…”