Y.M Dai, LPEM and National Laboratory for Superconductivity

Jeudi 28 Avril 2011, 16h00
Amphi Boreau, Esc C, 2ème etage

Optical properties of electron and hole-doped 122 iron-arsenic superconductors

Y.M.Dai1 ;2, R.P.S.M.Lobo1, A.Forget1, D.Colson1, B.Xu2, H.H.Wen2,
X.G.Qiu2

1LPEM, UPMC, ESPCI-ParisTech, CNRS, 10 rue Vauquelin, F-75231 Paris
Cedex 5, France
2National Laboratory for Superconductivity, Beijing National Laboratory for
Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences,
Beijing 100190, China

Superconductivity in the iron-arsenic compounds have various interesting aspects. One of the most distinguishing features of this family of superconductors is that a set of Fe 3d bands are crossing the Fermi Level and can participate in the forming of the cooper pairs. Multiple superconducting gaps may exist in iron-arsenic superconductors.
We present optical conductivity measurements on the electron-doped 122 system Ba(Fe1-xCox)2As2 and hole-doped 122 system Ba1-xKxFe2As2 single crystals. In both samples, a clear signature of the superconducting gap is observed when the temperature is below Tc, but a simple s-wave description fails in accounting for the low-frequency response. In the electron-doped sample Ba(Fe1-xCox)2As2, the data and the model can be reconciled by introducing an additional Drude peak which accounts for the additional low energy absorption. In the hole-doped sample Ba1¡xKxFe2As2, the low-frequency optical response can be well described by introducing a second isotropic superconducting gap which is a strong evidence for the existence of multiple superconducting gaps in iron-arsenic superconductors.

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