Type II superconductivity in SrPd2Ge2

TL;DR

This study uses scanning tunneling microscopy and spectroscopy to reveal the vortex lattice and confirm SrPd2Ge2 as a strong type II superconductor in the dirty limit, expanding understanding of its superconducting properties.

Contribution

It demonstrates the vortex lattice structure and confirms the type II nature of SrPd2Ge2 using tunneling spectroscopy and magnetization measurements, highlighting the dirty limit condition.

Findings

SrPd2Ge2 is a strong type II superconductor with   >>  .

Vortex lattice observed via STM confirms type II superconductivity.

Superconductivity in SrPd2Ge2 is induced by the dirty limit condition.

Abstract

Previous investigations have shown that SrPd2Ge2, a compound isostructural with "122" iron pnictides but iron- and pnictogen-free, is a conventional superconductor with a single s-wave energy gap and a strongly three-dimensional electronic structure. In this work we reveal the Abrikosov vortex lattice formed in SrPd2Ge2 when exposed to magnetic field by means of scanning tunneling microscopy and spectroscopy. Moreover, by examining the differential conductance spectra across a vortex and estimating the upper and lower critical magnetic fields by tunneling spectroscopy and local magnetization measurements, we show that SrPd2Ge2 is a strong type II superconductor with \kappa >> sqrt(2). Also, we compare the differential conductance spectra in various magnetic fields to the pair breaking model of Maki - de Gennes for dirty limit type II superconductor in the gapless region. This way we demonstrate that the type II superconductivity is induced by the sample being in the dirty limit, while in the clean limit it would be a type I superconductor with \kappa\ << sqrt(2), in concordance with our previous study (T. Kim et al., Phys. Rev. B 85, (2012)).