Microwave Spectroscopy of PrOs_4Sb_12: Josephson-Coupled Two-Band Superconductivity and Itinerant f Electrons

TL;DR

This study uses microwave surface impedance measurements to reveal two-band superconductivity with Josephson coupling in PrOs_4Sb_12 and demonstrates the itinerant nature of Pr f electrons through quasiparticle analysis.

Contribution

It provides direct microwave evidence for two-band superconductivity with Josephson coupling and characterizes the itinerant f electrons in PrOs_4Sb_12.

Findings

Evidence for two-band superconductivity with same symmetry order parameters.

Confirmation of Josephson pair-tunneling between bands.

Observation of heavily renormalized quasiparticles indicating itinerant f electrons.

Abstract

We report microwave surface impedance measurements made on a single crystal of PrOs_4Sb_12 across the frequency range 0.5 to 21 GHz. The penetration depth data provide clear thermodynamic evidence for superconductivity arising in two bands coupled by Josephson pair-tunneling, indicating two order parameters with the same symmetry. Detailed conductivity spectra obtained using high-resolution bolometry confirm this picture and extend it, revealing the itinerant nature of the Pr f electrons through the observation of quasiparticles with heavily renormalized mass.