Possible Multigap Superconductivity in the Heavy Fermion Ferromagnetic Superconductor UCoGe Revealed by Thermal Conductivity Measurements
We performed thermal conductivity measurements on a single crystal of the ferromagnetic superconductor UCoGe under magnetic field. Two different temperature dependencies of the thermal conductivity are observed, for H//b: linear at low magnetic field and quadratic for magnetic field larger than 1T. A the same field value, a plateau appears in the field dependence of the residual term of thermal conductivity. Such observations suggest a multigap superconductivity with a line of nodes in the superconducting gap.