Microscopic Mechanism and Pairing Symmetry of Superconductivity in the Noncentrosymmetric Heavy Fermion Systems CeRhSI$_3$ and CeIrSi$_3$

TL;DR

This paper investigates the pairing symmetry in noncentrosymmetric heavy fermion superconductors CeRhSi3 and CeIrSi3, revealing a mixed s-wave and p-wave state with line nodes, driven by antiferromagnetic spin fluctuations.

Contribution

It demonstrates that a mixed extended s-wave and p-wave pairing state, rather than d+f wave, is favored in these materials under pressure, based on Eliashberg equation solutions.

Findings

The gap function has line nodes on the Fermi surface.

The density of states resembles that of d-wave superconductors.

The NMR relaxation rate shows no coherence peak and varies as T^2 at low temperatures.

Abstract

We study the pairing symmetry of the noncentrosymmetric heavy fermion superconductors CeRhSi$_3$ and CeIrSi$_3$ under pressures, which are both antiferromagnets at ambient pressure. We solve the Eliashberg equation by means of the random phase approximation and find that the mixed state of extended s-wave and p-wave rather than the $d+f$ wave state could be realized by enhanced antiferromagnetic spin fluctuations. It is elucidated that the gap function has line nodes on the Fermi surface and the resulting density of state in the superconducting state shows a similar character to that of usual d-wave superconductors, resulting in the NMR relaxation rate $1/(T_1T)$ that exhibits no coherence peak and behaves like $1/(T_1T)\propto T^2$ at low temperatures.