Multiband superconductivity in the correlated electron filled skutterudite system Pr(1-x)Ce(x)Pt4Ge12

TL;DR

This study investigates how Ce substitution affects multiband superconductivity in Pr(1-x)Ce(x)Pt4Ge12, revealing suppression of Tc and a transition from nodal to nodeless gaps with increasing Ce content.

Contribution

It provides the first thermodynamic analysis showing the evolution from multiband nodal to nodeless superconductivity in Pr(1-x)Ce(x)Pt4Ge12 with Ce doping.

Findings

Superconducting transition temperature decreases with Ce substitution.

Superconductivity involves at least two bands with different gap structures.

Higher Ce levels lead to a fully gapped, nodeless superconducting state.

Abstract

Studies of superconductivity in multiband correlated electronic systems has become one of the central topics in condensed matter/materials physics. In this paper, we present the results of thermodynamic measurements on the superconducting filled skutterudite system Pr$_{1-x}$Ce$_x$Pt$_4$Ge$_{12}$ ($ 0 \leq x \leq 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 $T_{c}\sim 7.9$ K for $x=0$ to $T_c\sim 0.6$ K for $x=0.14$. Our analysis of the specific heat data for $x\leq 0.07$ 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 gap values decrease, with the nodal gap being suppressed more strongly, with Ce substitution. Ultimately, the higher Ce concentration samples ($x>0.07$) display a nodeless gap only.