Nuclear spin-lattice relaxation rate in noncentrosymmetric superconductors Y2C3

For a noncentrosymmetric superconductor such as Y2C3, we consider a parity-mixing model composed of spin-singlet s-wave and spin-triplet f-wave pairing components. The d-vector inf-wave state is chosen to be parallel to the Dresselhaus asymmetric spin-orbit coupling vector. It is found that, the quasiparticle excitation spectrum exhibits distinct nodal structure as a consequence of parity-mixing. We demonstrate particularly that such a model can qualitatively account for the existing experimental results of the temperature dependence of the nuclear spin-lattice relaxation rate T-1(-1) in Y2C3.