Nodeless time-reversal symmetry breaking in the centrosymmetric superconductor Sc$_5$Co$_4$Si$_{10}$ probed by muon-spin spectroscopy

A. Bhattacharyya; M. R. Lees; K. Panda; P. P. Ferreira; T. T. Dorini; Emilie Gaudry; L. T. F. Eleno; V. K. Anand; J. Sannigrahi; P. K. Biswas; R. Tripathi; D. T. Adroja

doi:10.1103/physrevmaterials.6.064802

arXiv · 2205.09609

Nodeless time-reversal symmetry breaking in the centrosymmetric superconductor Sc$_5$Co$_4$Si$_{10}$ probed by muon-spin spectroscopy

A. Bhattacharyya·M. R. Lees·K. Panda·P. P. Ferreira·T. T. Dorini·Emilie Gaudry·L. T. F. Eleno·V. K. Anand·J. Sannigrahi·P. K. Biswas·R. Tripathi·D. T. Adroja

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Abstract

We investigate the superconducting properties of Sc$_{5}$Co$_{4}$Si$_{10}$ using low-temperature resistivity, magnetization, heat capacity, and muon-spin rotation and relaxation ($\mu$SR) measurements. We find that Sc$_{5}$Co$_{4}$Si$_{10}$ {exhibits type-II} superconductivity with a superconducting transition temperature $T_\mathrm{C}= 3.5 (1)$\,K. The temperature dependence of the superfluid density obtained from transverse-field $\mu$SR spectra is best modeled using an isotropic Bardeen-Cooper-Schrieffer type $s$-wave gap symmetry with $2\Delta/k_\mathrm{B}T_\mathrm{C} = 2.84(2)$. However, the zero-field muon-spin relaxation asymmetry reveals the appearance of a spontaneous magnetic field below $T_\mathrm{C}$, indicating that time-reversal symmetry (TRS) is broken in the superconducting state. Although this behavior is commonly associated with non-unitary 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.

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A. Bhattacharyya, M. R. Lees, K. Panda, P. P. Ferreira, T. T. Dorini, Emilie Gaudry, L. T. F. Eleno, V. K. Anand, J. Sannigrahi, P. K. Biswas, R. Tripathi, D. T. Adroja. 2022-05-19. Nodeless time-reversal symmetry breaking in the centrosymmetric superconductor Sc$_5$Co$_4$Si$_{10}$ probed by muon-spin spectroscopy. https://doi.org/10.1103/physrevmaterials.6.064802

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