Andreev reflection spectroscopy on the heavy-fermion superconductor PrOs$_{4}$Sb$_{12}$: Microscopic evidence for multiple superconducting order parameters

TL;DR

This study uses point-contact Andreev reflection spectroscopy to investigate the superconducting gap structure of PrOs$_{4}$Sb$_{12}$, revealing evidence for multiple order parameters, including nodal and non-nodal gaps, and their evolution under magnetic fields.

Contribution

It provides microscopic evidence for multiple superconducting order parameters in PrOs$_{4}$Sb$_{12}$, including the identification of nodal and non-nodal gaps and their phase diagram.

Findings

Detection of multiple spectral features indicating multiple gaps.

Evidence of a nodal gap with zero-bias peaks.

Observation of a non-nodal gap in Ru-doped samples.

Abstract

Point-contact Andreev reflection spectroscopy was performed on single crystals of the heavy-fermion superconductor PrOs$_{4}$Sb$_{12}$, down to 90mK and up to 3Tesla. The conductance spectra showed multiple structures, including zero-bias peaks and spectral dips, which are interpreted as signatures of multiple pairing gaps, one clearly having nodes. Samples with 2% Ru replacing Os were also measured, showing pronounced spectral humps consistent with the emergence of a non-nodal gap. Detailed analysis of the spectral evolution revealed a magnetic field-\emph{vs.}-temperature phase diagram for PrOs$_{4}$Sb$_{12}$ characterized by two distinct superconducting order parameters.