Evidence for two-gap superconductivity in Ba0.55K0.45Fe2As2 from directional point-contact Andreev-reflection spectroscopy

TitleEvidence for two-gap superconductivity in Ba0.55K0.45Fe2As2 from directional point-contact Andreev-reflection spectroscopy
Publication TypeJournal Article
Year of Publication2009
AuthorsSzabo P, Pribulova Z, Pristas G, Bud'ko SL, Canfield PC, Samuely P
Journal TitlePhysical Review B
Volume79
Pages012503
Date Published01/01
ISBN Number1098-0121
Accession NumberISI:000262977900020
Keywordsbarium compounds, gaps, high-temperature superconductors, iron compounds, point contacts, potassium compounds, reflectivity, superconducting energy gap, superconducting transition temperature
Abstract

Directional point-contact Andreev-reflection spectroscopy measurements on the Ba0.55K0.45Fe2As2 single crystals are presented. The spectra show significant differences when measured in the ab plane in comparison with those measured in the c direction of the crystal. In the latter case only a reduced point-contact conductance around zero bias has been revealed persisting well above T-c and probably related to the structural and magnetic transitions in the system. Within the ab plane two superconducting energy gaps are detected below T-c. Here a reduced conductance above T-c could also be found. The fits of the ab-plane data to the superconducting s-wave two-gap model indicate that the smaller gap has a size below the BCS value while the large gap reveals much higher coupling strength.

URL<Go to ISI>://000262977900020
DOI10.1103/Physrevb.79.012503