Influence of multiband sign-changing superconductivity on vortex cores and vortex pinning in stoichiometric high- T c CaKFe 4 As 4

We use a scanning tunneling microscope to study the superconducting density of states and vortex lattice of single crystals of CaKFe4As4. This material has a critical temperature of Tc=35 K, one of the highest among stoichiometric iron based superconductors (FeBSCs), and is comparable to Tc found ne...

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Bibliographic Details
Authors: Fente, Antón, Meier, William R., Kong, Tai, Kogan, Vladimir G., Bud'Ko, Sergey L., Canfield, Paul C., Guillamón Gómez, Isabel, Suderow Rodríguez, Hermann Jesús
Format: article
Publication Date:2018
Country:España
Institution:Universidad Autónoma de Madrid
Repository:Biblos-e Archivo. Repositorio Institucional de la UAM
Language:English
OAI Identifier:oai:repositorio.uam.es:10486/689760
Online Access:http://hdl.handle.net/10486/689760
https://dx.doi.org/10.1103/PhysRevB.97.134501
Access Level:Open access
Keyword:Multiband superconductivity
Vortices in superconductors
Type-II superconductors
Scanning tunneling spectroscopy
Física
Description
Summary:We use a scanning tunneling microscope to study the superconducting density of states and vortex lattice of single crystals of CaKFe4As4. This material has a critical temperature of Tc=35 K, one of the highest among stoichiometric iron based superconductors (FeBSCs), and is comparable to Tc found near optimal doping in other FeBSCs. We observe quasiparticle scattering from defects with a pattern related to interband scattering between zone centered hole sheets. We measure the tunneling conductance in vortex cores and find a peak due to Caroli-de Gennes-Matricon bound states. The peak is located above the Fermi level, showing that CaKFe4As4 is a clean superconductor with vortex core bound states close to the so-called extreme quantum limit. We identify locations where the superconducting order parameter is strongly suppressed due to pair breaking. Vortices are pinned at these locations, and the length scale of the suppression of the order parameter is of order of the vortex core size. As a consequence, the vortex lattice is disordered up to 8 T.

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