Probing the superconducting ground state of noncentrosymmetric high entropy alloys using muon-spin rotation and relaxation

TL;DR

This study investigates the microscopic superconducting properties of noncentrosymmetric high entropy alloys using muon-spin techniques, revealing nodeless gaps and preserved time-reversal symmetry despite high disorder.

Contribution

First detailed characterization of superconducting properties in noncentrosymmetric HEAs using muon-spin rotation and relaxation methods.

Findings

Superconducting gap is nodeless and isotropic.

Time-reversal symmetry is preserved in the superconducting state.

Disordered HEAs can host conventional superconductivity.

Abstract

Recently, high entropy alloys (HEAs) have emerged as a new platform for discovering superconducting materials and offer avenues to explore exotic superconductivity. The highly disordered nature of HEA suggests regular phonon required for BCS superconductivity may be unlikely to occur. Therefore understanding the microscopic properties of these superconducting HEA is important. We report the first detailed characterization of the superconducting properties of the noncentrosymmetric ($\alpha$-Mn structure) HEA {(HfNb)}$_{0.10}${(MoReRu)}$_{0.90}$, and {(ZrNb)}$_{0.10}${(MoReRu)}$_{0.90}$ by using magnetization, specific heat, AC transport, and muon-spin relaxation/rotation ($\mu$SR). Despite the disordered nature, low temperature specific heat and transverse-field muon spin rotation measurements suggest nodeless isotropic superconducting gap and Zero-field $\mu$SR measurements confirm that time reversal symmetry is preserved in the superconducting ground state.