Nodeless superconductivity in the cage-type superconductor Sc5Ru6Sn18 with preserved time-reversal symmetry

D Kumar; C N Kuo; F Astuti; T Shang; M K Lee; C S Lue; I Watanabe; J A T Barker; T Shiroka; L J Chang

doi:10.1088/1361-648X/aacf65

Nodeless superconductivity in the cage-type superconductor Sc₅Ru₆Sn₁₈ with preserved time-reversal symmetry

J Phys Condens Matter. 2018 Aug 8;30(31):315803. doi: 10.1088/1361-648X/aacf65. Epub 2018 Jun 27.

Authors

D Kumar¹, C N Kuo, F Astuti, T Shang, M K Lee, C S Lue, I Watanabe, J A T Barker, T Shiroka, L J Chang

Affiliation

¹ Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan.

PMID: 29947614
DOI: 10.1088/1361-648X/aacf65

Abstract

We report the single-crystal synthesis and detailed investigations of the cage-type superconductor Sc₅Ru₆Sn₁₈, using powder x-ray diffraction (XRD), magnetization, specific-heat and muon-spin relaxation (µSR) measurements. Sc₅Ru₆Sn₁₈ crystallizes in a tetragonal structure (space group I4₁/acd) with lattice parameters a = 1.387(3) nm and c = 2.641(5) nm. Both DC and AC magnetization measurements prove the type-II superconductivity in Sc₅Ru₆Sn₁₈ with T _c ≈ 3.5(1) K, a lower critical field [Formula: see text] = 157(9) Oe and an upper critical field, [Formula: see text] = 26(1) kOe. The zero-field electronic specific-heat data are well fitted using a single-gap BCS model, with [Formula: see text] = 0.64(1) meV. The Sommerfeld constant γ varies linearly with the applied magnetic field, indicating s-wave superconductivity in Sc₅Ru₆Sn₁₈. Specific-heat and transverse-field (TF) µSR measurements reveal that Sc₅Ru₆Sn₁₈ is a superconductor with strong electron-phonon coupling, with TF-µSR also suggesting a single-gap s-wave character of the superconductivity. Furthermore, zero-field µSR measurements do not detect spontaneous magnetic fields below T _c, hence implying that time-reversal symmetry is preserved in Sc₅Ru₆Sn₁₈.