Possible two-gap superconductivity in NdFeAsO0.9F0.1 probed by point-contact Andreev-reflection spectroscopy

TitlePossible two-gap superconductivity in NdFeAsO0.9F0.1 probed by point-contact Andreev-reflection spectroscopy
Publication TypeJournal Article
Year of Publication2009
AuthorsSamuely P, Szabo P, Pribulova Z, Tillman ME, Bud'ko SL, Canfield PC
Journal TitleSuperconductor Science & Technology
Volume22
Pages014003
Date Published01/01
ISBN Number0953-2048
Accession NumberISI:000261761300005
Keywordsgaps, layered superconductor
Abstract

Systematic studies of the NdFeAsOF superconducting energy gap using point-contact Andreev-reflection (PCAR) spectroscopy are presented. At low temperatures the PCAR conductance spectra show a pair of gap-like peaks at about +/-(4-7) mV and in most cases also a pair of humps at around +/- 10 mV. Fits to the s-wave two-gap model of the PCAR conductance allowed to determine two superconducting energy gaps in the system. However, the energy-gap features disappear at T* = 15-20 K, much below the particular T-c of the junction under study. At T* a zero-bias conductance (ZBC) peak emerges, which at higher temperatures usually overwhelms the spectrum with an intensity significantly higher than the conductance signal at lower temperatures. Possible causes of this unexpected temperature effect are discussed. In some cases the conductance spectra show just a reduced conductance around the zero-bias voltage, the effect persisting well above the bulk transition temperature. This indicates the presence of a pseudogap in the system.

URL<Go to ISI>://000261761300005
DOI10.1088/0953-2048/22/1/014003