SrPt$_3$P: two-band single-gap superconductor

TL;DR

This study investigates the superconducting properties of SrPt$_3$P, revealing it as a two-band superconductor with a single energy gap but different coherence lengths, combining features of single-gap and multi-gap systems.

Contribution

The paper provides evidence that SrPt$_3$P is a two-band superconductor with equal gaps but different coherence lengths, based on muon-spin rotation measurements.

Findings

Single s-wave energy gap with $\\Delta=1.58$ meV

Field-dependent magnetic penetration depth

Upward curvature of upper critical field

Abstract

The magnetic penetration depth ($\lambda$) as a function of applied magnetic field and temperature in SrPt$_3$P($T_c\simeq8.4$ K) was studied by means of muon-spin rotation ($\mu$SR). The dependence of $\lambda^{-2}$ on temperature suggests the existence of a single $s-$wave energy gap with the zero-temperature value $\Delta=1.58(2)$ meV. At the same time $\lambda$ was found to be strongly field dependent which is the characteristic feature of the nodal gap and/or multi-gap systems. The multi-gap nature of the superconduicting state is further confirmed by observation of an upward curvature of the upper critical field. This apparent contradiction would be resolved with SrPt$_3$P being a two-band superconductor with equal gaps but different coherence lengths within the two Fermi surface sheets.