Evidence for Line Nodes in the Superconducting Energy Gap of Noncentrosymmetric CePt_3Si from Magnetic Penetration Depth Measurements

摘要

We report measurements of the magnetic penetration depth λ(T) in high-quality CePt_3Si samples down to 0.049 K. We observe a linear temperature dependence below T approx= 0.16 T_C, which is interpreted as evidence for line nodes in the energy gap of the low-temperature phase of this material. A kink in λ(T) at about 0.53 K may be associated with the second superconducting transition recently reported. The results are discussed in terms of the symmetry of the superconducting order parameter.