Multiband superconductivity in the correlated electron filled skutterudite systemPr1−xCexPt4Ge12

Studies of superconductivity in multiband correlated electronic systems have become one of the central topics in condensed-matter and materials physics. In this paper, we present the results of thermodynamic measurements on the superconducting filled skutterudite system ${\mathrm{Pr}}_{1\ensuremath{-}x}{\mathrm{Ce}}_x{\mathrm{Pt}}₄{\mathrm{Ge}}₁₂$ $(0\ensuremath{\le}x\ensuremath{\le}0.2)$ to investigate how substitution of Ce at Pr sites affects superconductivity. We find that an increase in Ce concentration leads to a suppression of the superconducting transition temperature from ${T}_c\ensuremath{\sim}7.9$ K for $x=0$ to ${T}_c\ensuremath{\sim}0.6$ K for $x=0.14$. Our analysis of the specific-heat data for $x\ensuremath{\le}0.07$ reveals that superconductivity must develop in at least two bands: the superconducting order parameter has nodes on one Fermi pocket and remains fully gapped on the other. Both the nodal and nodeless gaps decrease, with the nodal gap being suppressed more strongly upon Ce substitution. Ultimately, the higher-Ce-concentration samples $(x>0.07)$ display a nodeless gap only.