Disorder-induced unconventional superconductivity in pseudo-binary α-Mn alloy

Significant efforts have been devoted to understanding the pairing mechanisms in non-centrosymmetric superconductors with α-Mn crystal structures, which provide an ideal platform for studying how antisymmetric spin-orbit coupling and time-reversal symmetry (TRS) breaking affect systems that are weakly connected. In this study, we report the synthesis of a new non-centrosymmetric α-Mn superconductor, NbTaOs₂, exhibiting a superconducting transition temperature of 2.4(2) K. A comprehensive investigation of its superconducting properties was carried out using resistivity, magnetization, specific heat, and muon spin relaxation and rotation (μSR) measurements.

Recent theoretical work has proven that magnetic fields can emerge from disorder in the superconducting state, particularly when TRS breaking occurs in the bulk or near regions of spatial inhomogeneity. The results from transverse field-μSR, in combination with electronic specific heat data, indicate a strongly coupled superconducting state with a BCS-type single-gap in NbTaOs₂. Furthermore, zero-field μSR measurements reveal a significant rise in the relaxation rate, suggesting the presence of a weak spin-triplet component in the superconducting ground state. This observation points to the pivotal role of the disorder contributing to weak TRS-breaking signals.