No abstract

Noncentrosymmetric superconductors with α-manganese structure has attracted much attention recently, after the discovery of time-reversal symmetry breaking in all the members of Re6X (X = Ti, Hf, Zr) family. Similar to Re6X, NbOs2 also adopts α-M n structure and found to be superconducting with critical temperature Tc 2.7 K. The results of the resistivity, magnetization, specific heat and muon-spin relaxation/rotation measurements show that NbOs2 is a weakly coupled type-II superconductor. Interestingly, the zero-field muon experiments indicate that the time-reversal symmetry is preserved in the superconducting state. The low-temperature transverse-field muon measurements and the specific heat data evidence an conventional isotropic fully gapped superconductivity. However, the calculated electronic properties in this material show that the NbOs2 is positioned close to the band of unconventionality of the Uemura plot, indicating that NbOs2 potentially borders an unconventional superconducting ground state. arXiv:1901.05630v1 [cond-mat.supr-con]

The nonsymmorphic Zr2Ir alloy is a possible topological semimetal candidate material and as such may be part of an exotic class of superconductors. Zr2Ir is a superconductor with a transition temperature of 7.4 K with critical fields of 19.6(3) mT and 3.79(3) T, as determined by heat capacity and magnetisation. Zero field muon spin relaxation measurements show that time-reversal symmetry is preserved in these materials. The specific heat and transverse field muon spin rotation measurements rule out any possibility to have a nodal or anisotropic superconducting gap, revealing a conventional s-wave nature in the superconducting ground state. Therefore, this system is found to be conventional nonsymmorphic superconductor, with time-reversal symmetry being preserved and an isotropic superconducting gap.

Noncentrosymmetric superconductors can lead to a variety of exotic properties in the superconducting state such as line nodes, multigap behavior, and time-reversal symmetry breaking. In this paper, we report the properties of the new noncentrosymmetric superconductor TaOs, using muon spin relaxation and rotation measurements. It is shown using the zero-field muon experiment that TaOs preserve the time-reversal symmetry in the superconducting state. From the transverse field muon measurements, we extract the temperature dependence of λ(T ) which is proportional to the superfluid density. This data can be fit with a fully gapped s-wave model for α = ∆(0)/kBTc = 2.01 ± 0.02. Furthermore, the value of magnetic penetration depth is found to be 5919 ± 45 Å, which is consistent with the value obtained from the bulk measurements.

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