Microscopic studies of the normal and superconducting state of Ca3Ir4Sn13

TL;DR

This study uses muon spin rotation to investigate the magnetic and superconducting properties of Ca3Ir4Sn13, revealing a non-magnetic normal state and strong-coupling, nodeless superconductivity without evidence of magnetic fluctuations.

Contribution

It provides the first muSR evidence that the anomaly at T* is non-magnetic and characterizes the superconducting state as strong-coupling and nodeless in Ca3Ir4Sn13.

Findings

No evidence of spin fluctuations in the normal state.

Superconductivity is strong-coupling and nodeless.

The anomaly at T* is not magnetic in origin.

Abstract

We report on muon spin rotation (muSR) studies of the superconducting and magnetic properties of the ternary intermetallic stannide Ca3Ir4Sn13. This material has recently been the focus of intense research activity due to a proposed interplay of ferromagnetic spin fluctuations and superconductivity. In the temperature range T=1.6-200 K, we find that the zero-field muon relaxation rate is very low and does not provide evidence for spin fluctuations on the muSR time scale. The field-induced magnetization cannot be attributed to localized magnetic moments. In particular, our muSR data reveal that the anomaly observed in thermal and transport properties at T*~38 K is not of magnetic origin. Results for the transverse-field muon relaxation rate at T=0.02-12 K, suggest that superconductivity emerges out of a normal state that is not of a Fermi-liquid type. This is unusual for an electronic system lacking partially filled f-electron shells. The superconducting state is dominated by a nodeless order parameter with a London penetration depth of lambda=385(1) nm and the electron-phonon pairing interaction is in the strong-coupling limit.