Evidence for conventional superconductivity in SrPd2Ge2

TL;DR

This study provides evidence that SrPd2Ge2 is a conventional superconductor with an s-wave gap, distinct from iron-based superconductors, supported by ARPES, STS, and band-structure calculations showing its electronic properties.

Contribution

The paper demonstrates that SrPd2Ge2 exhibits conventional superconductivity with a small band renormalization, contrasting with the strongly correlated iron pnictides.

Findings

Single s-wave superconducting gap of 0.5 meV

Weak band renormalization factor of 0.95

Strongly three-dimensional Fermi surface character

Abstract

Electronic structure of SrPd2Ge2 single crystals is studied by angle-resolved photoemission spectroscopy (ARPES), scanning tunneling spectroscopy (STS) and band-structure calculations within the local-density approximation (LDA). The STS measurements show single s-wave superconducting energy gap \Delta(0) = 0.5 meV. Photon-energy dependence of the observed Fermi surface reveals a strongly three-dimensional character of the corresponding electronic bands. By comparing the experimentally measured and calculated Fermi velocities a renormalization factor of 0.95 is obtained, which is much smaller than typical values reported in Fe-based superconductors. We ascribe such an unusually low band renormalization to the different orbital character of the conduction electrons and using ARPES and STS data argue that SrPd2Ge2 is likely to be a conventional superconductor, which makes it clearly distinct from isostructural iron pnictide superconductors of the "122" family.