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Two-gap superconductivity in the Fe-1111 superconductor LaFeAsO1â?’x F x : A point-contact Andreev-reflection study |
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| Authors: | Renato S Gonnelli Mauro Tortello Dario Daghero Giovanni Alberto Ummarino Valeri A Stepanov Jun S Kim |
| Institution: | 1. Dipartimento di Fisica and CNISM, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129, Torino, Italy 2. P. N. Lebedev Physical Institute, Russian Academy of Sciences, Leninskiy Prospekt 53, 119991, Moscow, Russia 3. Max-Planck-Institut f??r Festk??rperforschung, Heisenbergstra??e 1, D-70569, Stuttgart, Germany |
| Abstract: | Point-contact Andreev-reflection (PCAR) experiments were performed in the Fe-1111 layered superconductor LaFeAsO0.9F0.1 with resistive T c on ∼ 27 K. The observation of two pairs of peaks in the low-temperature Andreev-reflection spectra clearly indicates the presence of two order parameters. The behavior of the two gaps as a function of temperature, obtained by fitting the conductance curves by means of the generalized two-band Blonder-Tinkham-Klapwijk model, shows some anomalies. A theoretical analysis performed within the two-band Eliashberg theory with a generic electron-boson coupling can reproduce the low-temperature value of the two gaps but generally fails in giving a satisfactory fit of their overall temperature dependence, indicating the rich and complex physics of these newly discovered superconductors. |
| Keywords: | Fe-based superconductors point-contact Andreev-reflection spectroscopy two-band Eliashberg theory |
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