Thermal conductivity evidence for d_{x^2-y^2} pairing symmetry in the heavy-fermion CeIrIn5 superconductor

TL;DR

This study uses thermal transport measurements to determine the superconducting gap symmetry in CeIrIn5, revealing a d_{x^2-y^2} pairing symmetry in the second superconducting dome, suggesting a common magnetic fluctuation-mediated mechanism.

Contribution

The paper provides direct experimental evidence of d_{x^2-y^2} pairing symmetry in CeIrIn5's second superconducting dome, clarifying its gap structure and pairing mechanism.

Findings

Fourfold oscillation observed in ab-plane magnetic field rotation

No oscillation observed in bc-plane rotation

Results support d_{x^2-y^2} pairing symmetry

Abstract

Quasi-two dimensional CeIrIn5 contains two distinct domes with different heavy fermion superconducting states in its phase diagram. Here we pinned down the superconducting gap structure of CeIrIn5 in the second dome, located away from the antiferromagnetic quantum critical point, by the thermal transport measurements in magnetic fields rotated relative to the crystal axes. Clear fourfold oscillation was observed when the field is rotated within the ab-plane, while no oscillation was observed within the bc-plane. In sharp contrast to previous reports, our results are most consistent with d_{x^2-y^2} symmetry, implying that two superconducting phases have the same gap symmetry which appears to be mediated by antiferromagnetic spin fluctuations.