Multiband Superconductivity in Heavy Fermion Compound CePt_3Si without Inversion Symmetry : An NMR Study on a High-Quality Single Crystal(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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We report on novel superconducting characteristics of the heavy fermion (HF) superconductor CePt_3Si without inversion symmetry through ^<195>Pt-NMR study on a single crystal with T_c=0.46K that is lower than T_c〜0.75K for polycrystals. We show that the intrinsic superconducting characteristics inherent to CePt_3Si can be understood in terms of the unconventional strong-coupling state with a line-node gap below T_c=0.46K. The mystery about the sample dependence of T_c is explained by the fact that more or less polycrystals and single crystals inevitably contain some disordered domains, which exhibit a conventional BCS s-wave superconductivity (SC) below 0.8K In contrast, the Neel temperature T_N〜2.2K is present regardless of the quality of samples, revealing that the Fermi surface responsible for SC differ from that for the antiferromagnetic order. These unusual characteristics of CePt_3Si can be also described by a multiband model; in the homogeneous domains, the coherent HF bands are responsible for the unconventional SC, whereas in the disordered domains the conduction bands existing commonly in LaPt_3Si may be responsible for the conventional s-wave SC. We remark that some impurity scatterings in the disordered domains break up the 4f-electrons-derived coherent bands but not others. In this context, the small peak in 1/T_1 just below T_c reported before [Yogi et al. (2004)] is not due to a two-component order parameter composed of spin-singlet and spin-triplet Cooper pairing states, but due to the contamination of the disorder domains which are in the s-wave SC state.
社団法人日本物理学会の論文
2009-01-15

Multiband Superconductivity in Heavy Fermion Compound CePt_3Si without Inversion Symmetry : An NMR Study on a High-Quality Single Crystal(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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