Superconducting gap symmetry of the noncentrosymmetric superconductor W3Al2C

TL;DR

This study uses muon spin relaxation/rotation experiments to investigate the superconducting gap symmetry of W3Al2C, confirming it as a fully gapped, weakly-coupled superconductor that preserves time-reversal symmetry.

Contribution

It provides the first detailed muon spin relaxation/rotation analysis of W3Al2C, revealing its fully gapped spin-singlet superconducting state despite its non-centrosymmetric structure.

Findings

Superconductivity confirmed below 7.6 K via magnetization.

No spontaneous magnetic fields detected below Tc, preserving time-reversal symmetry.

Superfluid density analysis indicates a fully gapped, spin-singlet superconducting state.

Abstract

A detailed zero-field and transverse-field muon spin relaxation/rotation ($\mu$SR) experiemnts have been carried out on the recently discovered non-centrosymmetric superconductor W$_3$Al$_2$C to speculate about its superconducting ground state. Bulk nature of superconductivity below 7.6 K is confirmed through magnetization measurements. No change in the $\mu$SR spectra collected above and below $T_c$ is visible, ruling out the possibility of spontaneous magnetic field below $T_c$. This confirms that time-reversal symmetry is preserved for W$_3$Al$_2$C upon entering in the superconducting ground state. Temperature dependent superfluid density [$\rho_s(T)$], which directly reflects the superconducting gap symmetry is obtained by the analysis of spectra obtained from the transverse-field $\mu$SR experiments. Despite a non-centrosymmetric structure, W$_3$Al$_2$C adopts a fully gaped spin-singlet superconducting ground state with a zero temperature value of gap $\Delta_0$ = 1.158(8) meV with gap-to-$T_c$ ratio 2$\Delta_0/k_BT_c\approx$3.54, classifying this material as a weakly-coupled superconductors.