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Abstract:
Mixed spin-singlet and spin-triplet pairing can occur in noncentrosymmetric superconductors. In this respect, a comprehensive characterization of the noncentrosymmetric superconductor BeAu was carried out. It was established that BeAu undergoes a structural phase transition from a low-temperature noncentrosymmetric FeSi structure type to a high-temperature centrosymmetric structure in the CsCl type at T-s = 860 K. The low-temperature modification exhibits a superconducting transition below T-c = 3.3 K. The values of lower (H-c1 = 32 Oe) and upper (H-c2 = 335 Oe) critical fields are rather small, confirming that this type-II (kappa(G-L) = 2.3) weakly coupled (lambda(e-p) = 0.5, Delta C-e/gamma T-n(c) approximate to 1.26) superconductor can be well understood within the Bardeen-Cooper-Schrieffer theory. The muon spin relaxation analysis indicates that the time-reversal symmetry is preserved when the superconducting state is entered, supporting conventional superconductivity in BeAu. From the density functional band structure calculations, a considerable contribution of the Be electrons to the superconducting state was established. On average, a rather small mass renormalization was found, consistent with the experimental data.
