• 
  Bhattacharyya, A.; Lees, M.R.; Panda, K.; Ferreira, P.P.; Dorini, T.T.; Gaudry, E.; Eleno, L.T.F.; Anand, V.K.; Sannigrahi, J.; Biswas, P.K.; Tripathi, R.; Adroja, D.T.: Nodeless time-reversal symmetry breaking in the centrosymmetric superconductor Sc₅Co₄Si₁₀ probed by muon-spin spectroscopy. Physical Review Materials 6 (2022), p. 064802/1-10

10.1103/physrevmaterials.6.064802
Open Access Version (externer Anbieter)

Abstract:
We investigate the superconducting properties of Sc5Co4Si10 using low-temperature resistivity, magnetization, heat capacity, and muon-spin rotation and relaxation (μSR) measurements. We find that Sc5Co4Si10 exhibits type-II superconductivity with a superconducting transition temperature TC=3.5(1)K. The temperature dependence of the superfluid density obtained from transverse-field μSR spectra is best modeled using an isotropic Bardeen-Cooper-Schrieffer type s-wave gap symmetry with 2Δ/kBTC=2.84(2). However, the zero-field muon-spin relaxation rate reveals the appearance of a spontaneous magnetic field below TC, indicating that time-reversal symmetry (TRS) is broken in the superconducting state. Although this behavior is commonly associated with nonunitary or mixed singlet-triplet pairing, our group-theoretical analysis of the Ginzburg-Landau free energy alongside density functional theory calculations indicates that unconventional mechanisms are pretty unlikely. Therefore, we have hypothesized that TRS breaking may occur via a conventional electron-phonon process.