Resonances in thermal conductivity of superconducting CeCoIn₅ in rotating magnetic field

We performed thermal conductivity measurements of d-wave superconducting CeCoIn₅ in magnetic field up to 12 Tesla rotating in the a-b plane of this tetragonal compound, in a dilution refrigerator. The heat current J was applied along the [100] direction, antinodal of the superconducting order parameter. In similar previous measurements we observed sharp field-magnitude independent resonances in thermal conductivity for field direction Θ = ± 33° away from the direction of the heat current J applied along [110], the direction of the nodes. For heat current J||[100] we observe the resonances at Θ = ± 12°, complimentary to previous 33° resonances, also independent of the magnitude of the magnetic field. The field direction with respect to the crystallographic direction, not the direction of the heat current, is therefore of importance. Our model calculation of the density of state in the normal CeCoIn₅ in magnetic field show sharp resonances as function of the field orientation. This suggests that the sharp resonances in thermal conductivity in superconducting CeCoIn₅ should be attributed to normal parts of the Fermi surface, which were suggested to exist in magnetic field.