Effect of impurities on the low temperature NMR relaxation rate of a noncentrosymmetric superconductor

The spin–lattice relaxation rate of nuclear magnetic resonance (NMR) in a superconductor without inversion symmetry by considering a Cooper pairing model with a two-component order parameter composed of spin–singlet and spin–triplet pairing components in the presence of impurity effect is investigated. By using the Green’s function method and linear response theory we calculate the appropriate correlation function to evaluate the spin–lattice relaxation rate. For a noncentrosymmetric and clean superconductor such as CePt3Si a power law temperature dependence ( T 3 ) of the nuclear magnetic relaxation rate at low temperatures, suggests that the gap function has line nodes, consistent with this gap model. In a dirty superconductor the linear temperature dependence of the spin–lattice relaxation rate characteristic of the normal state Koringa relation.