Evidence for novel pairing state in noncentrosymmetric superconductor CePt3Si: Si-29-NMR knight shift study

We report the measurements of the Si-29 Knight shift K-29 on the noncentrosymmetric heavy-fermion compound CePt3Si in which antiferromagnetism (AFM) with T-N = 2.2 K coexists with superconductivity (SC) with T-c = 0.75 K. Its spin part K-29(s), which is deduced to be K-s(c) >= 0.11 and 0.16% at respective magnetic fields H = 2.0061 and 0.8671 T, does not decrease across the superconducting transition temperature Tc for the field along the c-axis. The temperature dependence of nuclear spin-lattice relaxation of Pt-195 below T-c has been accounted for by a Cooper pairing model with a two-component order parameter composed of spin-singlet and spin-triplet pairing components. From this result, it is shown that the Knight-shift data are consistent with the occurrence of the two-component order parameter for CePt3Si.