Unusual behaviours and impurity effects in the noncentrosymmetric superconductor CePt₃Si

Abstract

We report a study in which the effect of defects/impurities, growth process,\noff-stoichiometry, and presence of impurity phases on the superconducting\nproperties of noncentrosymmetric CePt3Si is analysed by means of the\ntemperature dependence of the magnetic penetration depth. We found that the\nlinear low-temperature response of the penetration depth -indicative of line\nnodes in this material- is robust regarding sample quality, in contrast to what\nis observed in unconventional centrosymmetric superconductors with line nodes.\nWe discuss evidence that the broadness of the superconducting transition may be\nintrinsic, though not implying the existence of a second superconducting\ntransition. The superconducting transition temperature systematically occurs\naround 0.75 K in our measurements, in agreement with resistivity and ac\nmagnetic susceptibility data but in conflict with specific heat, thermal\nconductivity and NMR data in which Tc is about 0.5 K. Random defects do not\nchange the linear low-temperature dependence of the penetration depth in the\nheavy-fermion CePt3Si with line nodes, as they do in unconventional\ncentrosymmetric superconductors with line nodes.\n