Modeling and photoabsorption study of YPd_2-xRh_xB₂C superconductors

The electronic structures of six polycrystalline borocarbide superconductors YPd_5-xRh_xB₃C_0.4 (x=0, 0.05, 0.1, 0.15, 0.2, and 0.25) were studied by photoemission and photoabsorption spectroscopies and theoretical calculations. The valence-band (VB) photoemission spectrum is compared with the theoretical total and partial density-of-states (DOS) curves. The Pd L₃-edge x-ray absorption near edge spectra (XANES) are compared with the calculated XANES spectra for these intermetallic compounds. The decrease of the superconducting transition temperatures (T_c) with addition of Rh dopant in these compounds is due to a decrease of the total DOS at the Fermi level (E_F).