in rotating magnetic field*

Thermal-conductivity measurements are a powerful method of studying superconductivity. Cooper pairs of the condensate do not carry heat, and only unpaired electrons participate in a heat transport. We have measured the thermal conductivity of unconventional superconductor CeCoIn₅ in a rotating magnetic field. At a sufficiently low temperature below 100 mK, multiple features, including sharp resonances, are observed in the thermal conductivity as a function of the direction of the magnetic field. This fine structure of thermal conductivity may come from the interaction between the magnetic field and normal electrons in this multiband superconductor. Our measurements represent a new way of studying the superconducting state of a material.