Conventional $s$-Wave Superconductivity in Noncentrosymmetric Ir$_2$Ga$_9$: $^{71}$Ga-NQR Evidence

TL;DR

This study uses $^{71}$Ga-NQR to demonstrate that noncentrosymmetric Ir$_2$Ga$_9$ exhibits conventional s-wave superconductivity with no signs of unconventional pairing despite lacking spatial centrosymmetry.

Contribution

It provides the first nuclear-quadrupole-resonance evidence showing conventional s-wave superconductivity in a noncentrosymmetric material, challenging expectations of unconventional pairing.

Findings

$^{71}$Ga-NQR shows a coherence peak below $T_c$

Superconductivity in Ir$_2$Ga$_9$ is conventional s-wave

No evidence of unconventional pairing due to ASOC

Abstract

We report a $^{71}$Ga nuclear-quadrupole-resonance (NQR) study on the characteristics of superconductivity in noncentrosymmetric Ir$_2$Ga$_9$ at zero field (H=0). The $^{71}$Ga-NQR measurements have revealed that $1/T_1$ has the clear coherence peak just below $T_{\rm c}$, and decreases exponentially upon further cooling in Ir$_2$Ga$_9$. From these results, Ir$_2$Ga$_9$ is concluded to be the conventional s-wave superconductor. Despite the lack of spatial centrosymmetry, there are no evidence for unconventional superconducting state ascribed to ASOC in Ir$_2$Ga$_9$.