Investigation of superconducting and normal-state properties of the filled-skutterudite system PrPt$_{4}$Ge$_{12-x}$Sb$_{x}$

TL;DR

This study investigates how substituting Sb for Ge in PrPt4Ge12 affects its superconducting properties, revealing suppression of superconductivity with increased Sb content and insights into the electronic and vibrational characteristics of the system.

Contribution

It provides new experimental data on the impact of Sb substitution on superconductivity and electronic structure in filled-skutterudite PrPt4Ge12-xSbx, including the role of rattling modes.

Findings

Superconductivity is suppressed with increasing Sb content, disappearing above x=4.

The Sommerfeld coefficient decreases with Sb substitution, indicating changes in electronic density of states.

Evidence of a weak rattling mode associated with Pr ions, but not linked to superconductivity suppression.

Abstract

We report a study of the superconducting and normal-state properties of the filled-skutterudite system PrPt$_{4}$Ge$_{12-x}$Sb$_x$. Polycrystalline samples with Sb concentrations up to $x =$ 5 were synthesized and investigated by means of x-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat measurements. We observed a suppression of superconductivity with increasing Sb substitution up to $x =$ 4, above which, no signature of superconductivity was observed down to 140 mK. The Sommerfeld coefficient, $\gamma$, of superconducting specimens decreases with increasing $x$ up to $x =$ 3, suggesting that superconductivity may depend on the density of electronic states in this system. The specific heat for $x =$ 0.5 exhibits an exponential temperature dependence in the superconducting state, reminiscent of a nodeless superconducting energy gap. We observed evidence for a weak "rattling" mode associated with the Pr ions, characterized by an Einstein temperature $\Theta_{\mathrm{E}} \sim$ 60 K for 0 $\leq x \leq$ 5; however, the rattling mode may not play any role in suppressing superconductivity.