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

TL;DR

This study synthesizes and characterizes the superconductor Sc5Ru6Sn18, revealing nodeless s-wave superconductivity with preserved time-reversal symmetry and strong electron-phonon coupling, based on comprehensive experimental measurements.

Contribution

It provides the first detailed investigation of the superconducting properties of Sc5Ru6Sn18, demonstrating nodeless s-wave pairing and preserved time-reversal symmetry in this cage-type superconductor.

Findings

Superconducting transition temperature Tc = 3.5 K.

Evidence of strong electron-phonon coupling.

Preservation of time-reversal symmetry in the superconducting state.

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 (muSR) measurements. Sc5Ru6Sn18 crystallizes in a tetragonal structure (space group I41/acd) with the 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 Tc = 3.5(1) K, a lower critical field H_c1 (0) = 157(9) Oe and an upper critical field, H_c2 (0) = 26(1) kOe. The zero-field electronic specific-heat data are well fitted using a single-gap BCS model, with superconducting gap = 0.64(1) meV. The Sommerfeld constant varies linearly with the applied magnetic field, indicating s-wave superconductivity in Sc5Ru6Sn18. Specific-heat and transverse-field (TF) muSR measurements reveal that Sc5Ru6Sn18 is a superconductor with strong electron-phonon coupling, with TF-muSR also suggesting the single-gap s-wave character of the superconductivity. Furthermore, zero-field muSR measurements do not detect spontaneous magnetic fields below Tc, hence implying that time-reversal symmetry is preserved in Sc5Ru6Sn18.