On Superconducting Double Transition in PrOs_4_Sb_12

TL;DR

This paper investigates the superconducting double transition in PrOs_4_Sb_12 by analyzing anisotropy in the upper critical field, proposing a weak spin-orbit triplet pairing state that breaks time-reversal symmetry as a likely explanation.

Contribution

It introduces a new analysis of the pairing state in PrOs_4_Sb_12, suggesting a weak spin-orbit triplet pairing state to explain the double transition.

Findings

Gradient coupling induces twofold oscillation of H_c2, conflicting with experiments.

Weak spin-orbit triplet pairing state avoids mixing effects.

Time-reversal symmetry is broken in the proposed pairing state.

Abstract

Superconducting double transition in PrOs_4_Sb_12 is investigated by analyzing the anisotropy of the upper critical field H_c2 in the ab-plane, and the possible pairing state is discussed. When mixing due to gradient coupling is active, the twofold-symmetric component is necessarily induced in the fourfold symmetric phase, leading to the twofold oscillation of H_c2, contrary to the experimental result. To avoid the mixing effect, the weak spin-orbit coupling triplet pairing state is considered as a likely pairing function, where time-reversal symmetry is broken.