Role of p-d hybridization in the Tc-variation of Y(Rh1-xRux)4B4 superconductors

Abstract Auger and photoemission studies for Y(Rh 1−x Ru x ) 4 B 4 superconductors elucidate the mechanism for the abrupt drop in T c near x =0.5. The B p -states admix more strongly with Ru than Rh d -states, thereby yielding low-T c values for Ru-rich compounds due to broadening of the d -band feutures. These effects underlie a previous suggestion that the preservation of Rh 4 tetrahedral units is essential for high-T c values in ternary boride compounds.