Point-contact spectroscopy in Co-doped CaFe2As2: nodal superconductivity and 
topological Fermi surface transition

Gonnelli, R. S.; Tortello, M.; Daghero, D.; Kremer, R. K.; Bukowski, Z.; Zhigadlo, N. D.; Karpinski, J.

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Point-contact spectroscopy in Co-doped CaFe₂As₂: nodal superconductivity and topological Fermi surface transition

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Gonnelli, R. S.
Former Scientific Facilities, Max Planck Institute for Solid State Research, Max Planck Society;

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Kremer, R. K.
Former Scientific Facilities, Max Planck Institute for Solid State Research, Max Planck Society;

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Citation

Gonnelli, R. S., Tortello, M., Daghero, D., Kremer, R. K., Bukowski, Z., Zhigadlo, N. D., et al. (2012). Point-contact spectroscopy in Co-doped CaFe₂As₂: nodal superconductivity and topological Fermi surface transition. Superconductor Science and Technology, 25(6): 065007.

Cite as: https://hdl.handle.net/21.11116/0000-000E-C2BE-1

Abstract

We performed point-contact Andreev-reflection spectroscopy measurements in Ca(Fe1-xCox)(2)As-2 single crystals with effective x = 0.060 +/- 0.005. The spectra of ab-plane contacts show a zero-bias maximum and broad shoulders at about 5-6 meV. Their fit with the three-dimensional Blonder-Tinkham-Klapwijk (BTK) model (making use of an analytical expression for the Fermi surface that mimics the one calculated from first principles) shows that this compound presents a large isotropic gap on the quasi-2D electronlike Fermi surface sheets and a smaller anisotropic (possibly nodal) gap on the 3D holelike Fermi surface pockets centered at the Z point in the Brillouin zone. These results nicely fit into the theoretical picture for the appearance of nodal superconductivity in 122 compounds.