TY - JOUR
T1 - On the superconducting symmetry of Fe-based systems - Impurity effect studies and neutron scattering measurements-
AU - Sato, Masatoshi
AU - Kobayashi, Yoshiaki
AU - Kawamata, Takayuki
AU - Yasui, Yukio
AU - Suzuki, Kazunori
AU - Itoh, M.
AU - Kajimoto, Ryoichi
AU - Ikeuchi, Kazuhiko
AU - Arai, M.
AU - Bourges, Phillipe
N1 - Funding Information:
The authors thank Prof. H. Kontani for fruitful discussion. The work is supported by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (JSPS) and Technology. It is also supported by Transformative Research-Project on Iron Pnictides of Japan Science and Technology Corporation (JST TRIP).
PY - 2013/7
Y1 - 2013/7
N2 - To identify the superconducting symmetry of Fe-based superconductors, we studied effects of nonmagnetic-impurities on T c, magnetic excitation spectra x″ and NMR 1/T 1 - T curve, which are sensitive to the relative signs between the order parameters on the disconnected Fermi surfaces in reciprocal space, because the symmetry is closely connected with the pairing mechanism: If the signs are opposite (symmetry S ±), the mechanism is considered to be a magnetic one, but when the signs are the same (symmetry S ++), a novel mechanism is plausible because the ordinary phonon mechanism cannot realize the T c value as high as ∼55 K found in Ln1111 (Ln=lanthanide). Results are as follows: (a) The very small rates of T c-suppression by impurity atoms M of LnFe1-yMyAs0.89-xF0.11+x (M=Ni, Co, Ru) can be explained only by S ++. (b) The x″-data for Ba(Fe, Co)2As2 (T c ∼ 23 K) and Ca-Fe-Pt-As crystals seem to be well explained by S ++ rather than by S ±. (c) The nuclear magnetic resonance data can be consistently understood by S ++, too. These results suggest the S ++ symmetry and a novel pairing mechanism, which can be considered to be related to the elastic softening of C66 induced by the orbital fluctuation of the system.
AB - To identify the superconducting symmetry of Fe-based superconductors, we studied effects of nonmagnetic-impurities on T c, magnetic excitation spectra x″ and NMR 1/T 1 - T curve, which are sensitive to the relative signs between the order parameters on the disconnected Fermi surfaces in reciprocal space, because the symmetry is closely connected with the pairing mechanism: If the signs are opposite (symmetry S ±), the mechanism is considered to be a magnetic one, but when the signs are the same (symmetry S ++), a novel mechanism is plausible because the ordinary phonon mechanism cannot realize the T c value as high as ∼55 K found in Ln1111 (Ln=lanthanide). Results are as follows: (a) The very small rates of T c-suppression by impurity atoms M of LnFe1-yMyAs0.89-xF0.11+x (M=Ni, Co, Ru) can be explained only by S ++. (b) The x″-data for Ba(Fe, Co)2As2 (T c ∼ 23 K) and Ca-Fe-Pt-As crystals seem to be well explained by S ++ rather than by S ±. (c) The nuclear magnetic resonance data can be consistently understood by S ++, too. These results suggest the S ++ symmetry and a novel pairing mechanism, which can be considered to be related to the elastic softening of C66 induced by the orbital fluctuation of the system.
KW - Fe pnictide superconductors
KW - Impurity effects
KW - Magnetic excitation spectra
KW - NMR
KW - Superconducting symmetry
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U2 - 10.3938/jkps.62.1726
DO - 10.3938/jkps.62.1726
M3 - Article
AN - SCOPUS:84880033421
SN - 0374-4884
VL - 62
SP - 1726
EP - 1733
JO - Journal of the Korean Physical Society
JF - Journal of the Korean Physical Society
IS - 12
ER -