Superconducting properties of Pr-based Filled skutterudite PrRu$_4$As$_{12}$

TL;DR

This study investigates the superconducting properties and crystal electric field levels of PrRu4As12, revealing s-wave superconductivity, quasiparticle mass enhancement, and the influence of CEF levels on superconducting behavior.

Contribution

It provides the first systematic analysis of superconductivity and CEF effects in PrRu4As12, highlighting the role of inelastic scattering in mass enhancement and superconducting transition temperature.

Findings

Superconductivity in PrRu4As12 is s-wave and in the clean limit.

The electronic specific heat coefficient indicates quasiparticle mass enhancement.

CEF levels influence quasiparticle mass and superconducting properties.

Abstract

We report on systematic study of superconducting characteristics and Pr crystalline-electric-field (CEF) levels of filled-skutterudite \pra ($T_{\rm c}$ = 2.33 K). The temperature dependences of the upper critical field $H_{\rm c2}$ and the Ginzburg-Landau (Maki) parameter $\kappa_2$ suggest an s-wave clean-limit superconductivity. The electronic specific heat coefficient $\gamma \sim 95$ mJ/K$^2$mol, being $\sim 1.5$ times larger than that for \lra, indicates $4f$-originating quasiparticle mass enhancement. Magnetic susceptibility $\chi(T)$ indicates that the CEF ground state is a $\Gamma_1$ singlet and a $\Gamma_4^{(1)}$ triplet first excited state lies at $\Delta_{\rm CEF}\sim 30$ K above. Systematic comparison among \pos, \prs, \pra and La-based reference compounds suggests that inelastic exchange- and aspherical-charge-scatterings of conduction electrons from CEF-split $4f$ levels play an essential role for the quasiparticle mass enhancement and the value of $T_{\rm c}$ in the Pr-based filled skutterudites.