Multiple gaps revealed by low temperature specific heat in the 1111-type CaFe0.88Co0.12AsF single crystals.

Low-temperature specific heat (SH) is measured on the 1111-type CaFe0.88 Co0.12AsF single crystals under different magnetic fields. A clear SH jump with the height Delta C/T vertical bar T-c = 10.4 mJ mol(-1) K-2 is observed at the superconducting transition temperature T-c. The electronic SH coefficient Delta gamma(B) increases linearly with the field below 5 T and a kink is observed around 5 T, indicating a multi-gap feature in the present system. Such a sign is also reflected in the T-c - B data. A detailed analysis shows that this behavior can be interpreted in terms of a two-gap scenario with the ratio Delta L/Delta(S) = 2.8-4.5.