Specific heat in magnetic fields and superconducting gap structure in FeSe1−xTex (0.6 ⩽ x ⩽ 1)

Abstract

Specific heat has been measured in magnetic fields at low temperatures down to 0.4K in the iron-chalcogenide superconductors of FeSe1−xTex, in order to investigate details of the superconducting (SC) gap. Using the two-gap model, it has been found that the smaller SC gap is significantly depressed by the application of magnetic field. Moreover, it has been found that the enhancement of the residual electronic-specific-heat-coefficient in the ground state by the application of magnetic field is much smaller than that expected for superconductors with the typical s-wave or d-wave SC paring symmetry. These results are discussed in relation to the multi-band effect in the iron-based superconductors.