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  4. The Order-Parameter Symmetry and Fermi Surface Topology of 122 Fe-Based Superconductors: A Point-Contact Andreev-Reflection Study
 
conference paper

The Order-Parameter Symmetry and Fermi Surface Topology of 122 Fe-Based Superconductors: A Point-Contact Andreev-Reflection Study

Gonnelli, R. S.
•
Tortello, M.
•
Daghero, D.
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2013
Journal Of Superconductivity And Novel Magnetism
3rd International Conference on Superconductivity and Magnetism (ICSM)

We report on the results of directional point-contact Andreev-reflection (PCAR) measurements in Ba(Fe1-x Co (x) )(2)As-2 single crystals and epitaxial c-axis oriented films with x=0.08 as well as in Ca(Fe1-x Co (x) )(2)As-2 single crystals with x=0.06. The PCAR spectra are analyzed within the two-band 3D version of the Blonder-Tinkham-Klapwijk model for Andreev reflection we recently developed, and that makes use of an analytical expression for the Fermi surface that mimics the one calculated within the Density-Functional Theory (DFT). The spectra in Ca(Fe0.94Co0.06)(2)As-2 unambiguously demonstrate the presence of nodes or zeros in the small gap. In Ba(Fe0.92Co0.08)(2)As-2, the ab-plane spectra in single crystals can be fitted by assuming two nodeless gaps, but this model fails to fit the c-axis ones in epitaxial films. All these results are discussed in comparison with recent theoretical predictions about the occurrence of accidental 3D nodes and the presence of "hot spots" in the gaps of 122 compounds.

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Type
conference paper
DOI
10.1007/s10948-012-2069-0
Web of Science ID

WOS:000317014500107

Author(s)
Gonnelli, R. S.
Tortello, M.
Daghero, D.
Pecchio, P.
Galasso, S.
Stepanov, V. A.
Bukowski, Z.
Zhigadlo, N. D.
Karpinski, J.
Iida, K.
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Date Issued

2013

Publisher

Springer

Publisher place

New York

Published in
Journal Of Superconductivity And Novel Magnetism
Total of pages

7

Volume

26

Issue

4

Start page

1331

End page

1337

Subjects

Point-contact spectroscopy

•

Andreev reflection

•

Fe-based superconductors

•

Order-parameter symmetry

•

Fermi surface topology

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LPMC  
Event nameEvent placeEvent date
3rd International Conference on Superconductivity and Magnetism (ICSM)

Istanbul, TURKEY

APR 29-MAY 04, 2012

Available on Infoscience
May 13, 2013
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/92132
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