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| VOLUME 93 (2011) | ISSUE 2 | PAGE 95 |
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Observation of Multi-Gap Superconductivity in GdO(F)FeAs by Andreev Spectroscopy
T. E. Shanygina
 , Ya. G. Ponomarev*, S. A. Kuzmichev*, M. G. Mikheev*, S. N. Tchesnokov*, O. E. Omel'yanovskii , A. V. Sadakov, Yu. F. Eltsev , A. S. Dormidontov, V. M. Pudalov , A. S. Usol'tsev, E. P. Khlybov  P.N. Lebedev Physical Institute RAS, 119991 Moscow, Russia*Department of Low Temperature Physics and Superconductivity, Moscow State University, 119991 Moscow, Russia +International Laboratory of High Magnetic Fields and Low Temperatures, 53-421 Wroclaw, Poland  Moscow Institute of Physics and Technology, 141700 Moscow, Russia Institute for High Pressure Physics RAS, 142190 Troitsk, Moscow district, Russia
Abstract
We have studied current-voltage characteristics of Andreev contacts in polycrystalline GdO0.88F0.12FeAs samples with bulk critical temperature Tc = (52.5  1) K using
break-junction technique. The data obtained cannot be described within the
single-gap approach and suggests the existence of a multi-gap
superconductivity in this compound. The large and small superconducting gap
values estimated at T = 4.2 K are  meV and
ΔS =  meV, respectively.
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