Probing the superconducting energy gap from infrared spectroscopy on a Ba0.6K0.4Fe2As2 single crystal with Tc=37 K.
We performed optical spectroscopy measurement on a superconducting Ba0.6K0.4Fe2As2 single crystal with T{c}=37 K. Formation of the superconducting energy gaps in the far-infrared reflectance spectra below T{c} is clearly observed. A flat and close to unity reflectance is observed roughly below 150 cm;{-1} for T<<T{c}, following an s-wave pairing line shape. A more rapid decrease occurs near 200 cm;{-1}, leading to a peak in the ratio of the reflectance at T<<T{c} over that for T>or=T{c}. We determined the absolute value of the penetration depth at 10 K as lambda approximately 2000+/-80 A. A spectral weight analysis shows that the Ferrell-Glover-Tinkham sum rule is satisfied at low energy scale, less than 6Delta.
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
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G
Li
W Z
WZ
Hu
J
J
Dong
Z
Z
Li
P
P
Zheng
G F
GF
Chen
J L
JL
Luo
N L
NL
Wang