Heat-Capacity Measurements of Energy-Gap Nodes of the Heavy-Fermion Superconductor CeIrIn5 Deep inside the Pressure-Dependent Dome Structure of its Superconducting Phase Diagram

TL;DR

This study uses heat capacity measurements under rotating magnetic fields to determine the nodal gap structure of CeIrIn5, revealing a d{x^2-y^2} order parameter with sign reversal inside its superconducting dome.

Contribution

It provides the first detailed experimental evidence of the nodal gap symmetry in CeIrIn5 under pressure, constraining theoretical models of its pairing mechanism.

Findings

Four-fold oscillation in heat capacity observed at 0.3 K

Sign reversal of oscillation between 1.50 and 0.90 GPa

Evidence for d{x^2-y^2} gap symmetry with nodes along [110]

Abstract

We use heat capacity measurements as a function of field rotation to identify the nodal gap structure of CeIrIn5 at pressures to 2.05 GPa, deep inside its superconducting dome. A four-fold oscillation in the heat capacity at 0.3 K is observed for all pressures but with its sign reversed between 1.50 and 0.90 GPa. On the basis of recent theoretical models for the field-angle dependent specific heat, all data, including the sign reversal, imply a d{x^2-y^2} order parameter with nodes along [110], which constrains theoretical models of the pairing mechanism in CeIrIn5.