Charge transfer and transition-metal cluster: Boron bonding in the bct superconducting Y(Rh1−xRux)4B4 system

Abstract

An analysis of the bonding and charge transfer as a function of transition-metal concentration is presented for the bct superconducting system $\mathrm{Y}{\left({\mathrm{Rh}}_{1-x}{\mathrm{Ru}}_x\right)}_4{\mathrm{B}}_4$. A sharp drop in the superconducting critical temperature $T_c$ from 9.5 K to below 1.0 K near a critical concentration is not reflected in the smooth, linear variation of the single-crystal lattice parameters and B-B interatomic distances. Analysis of the boron $\mathrm{KVV}$ Auger data indicates the boron $p$-like states near the Fermi energy are increasingly populated in a continuous manner with increasing $x$. We find no evidence of any abrupt changes in the electronic structure near $x_{\mathrm{cr}}$.