Field-angle dependence of the zero-energy density of states in the unconventional heavy-fermion superconductorCeCoIn5

Abstract

Field-angle-dependent specific heat measurements have been made on the heavy-fermion superconductorCeCoIn5 down to , in a magnetic field rotating in the tetragonalc-plane. A clear fourfold angular oscillation is observed in the specific heat with the minima(maxima) occurring along the [100] ([110]) directions. Oscillation persists down to low fields, thus directly proving the existence of gap nodes. The resultsindicate that the superconducting gap symmetry is most probably ofdxy type.