Competition between superconductivity and charge-density-wave ordering in theLu5Ir4(Si1−xGex)10alloy system

Abstract

We have performed bulk measurements such as dc magnetic susceptibility, electrical resistivity, and heat capacity on the pseudoternary alloys ${\mathrm{Lu}}_{5}{\mathrm{Ir}}_{4}{({\mathrm{Si}}_{1\ensuremath{-}x}{\mathrm{Ge}}_{x})}_{10}$ to study the interplay and competition between superconductivity and the charge-density-wave- (CDW) ordering transition. We track the evolution of the superconducting transition temperature ${T}_{\mathrm{SC}}$ and the CDW-ordering temperature ${T}_{\mathrm{CDW}}$ as a function of $x$ (concentration of Ge) $(0.0\ensuremath{\leqslant}\mathit{x}\ensuremath{\leqslant}\phantom{\rule{0.3em}{0ex}}1.0)$. We find that increasing $x$ (increasing disorder) suppresses the ${T}_{\mathrm{CDW}}$ rapidly with the concomitant increase in ${T}_{\mathrm{SC}}$. We present a temperature-concentration (or volume) phase diagram for this system and compare our results with earlier work on substitution at the Lu or Ir site to show how dilution at the Si site presents a different situation from these other works. The heat capacity data in the vicinity of the CDW transition has been analyzed using a model of critical fluctuations in addition to a mean-field contribution and a smooth lattice background. We find that the critical exponents change appreciably with increasing disorder. This analysis suggests that the strong-coupling and non-mean-field-like CDW transition in the parent compound ${\mathrm{Lu}}_{5}{\mathrm{Ir}}_{4}{\mathrm{Si}}_{10}$ changes to a mean-field-like transition with increasing Ge concentration.