2007年7月4日（星期三),下午3:30
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题  目：Spin Triplet Superconducting State in Non-centrosymmetric Compound
Li2Pt3B
报告人：Prof. Guo-qing Zheng
　　　 Department of Physics, Okayama University, Japan
　
地  点：物理所D楼210会议室
报告摘要：
  The spatial inversion symmetry breaking can have great impact on
superconductivity, spin Hall Effect and multiferroics. In this talk, I will
present our recent NMR studies on the pairing symmetry in non-centrosymmetric
superconductors Li2Pt3B and Li2Pd3B.
  The perovskite-like cubic compounds Li2Pt3B and Li2Pd3B are superconducting
at Tc=2.7 K and 7 K, respectively. Unlike non-centrosymmetric heavy fermion
compounds such as CePt3Si or UIr where magnetism is important, the electron
correlations are very weak, if any. Through 11B and 195Pt NMR measurements, we
find that the spin susceptibility remains unchanged across Tc in Li2Pt3B. With
decreasing temperature (T) below Tc, the spin-lattice relaxation rate 1/T1
decreases in proportion to T3 with no coherence peak. These results indicate
that the Cooper pair is in the spin-triplet state and that there exist line
nodes in the superconducting gap function [1]. They are in sharp contrast with
those in the isostructural Li2Pd3B which is a spin-singlet, s-wave
superconductor [2], and are ascribed to the enhanced spin-orbit coupling due to
the lack of spatial inversion symmetry. Our finding points to a new paradigm
where exotic superconductivity arises in the absence of strong electron-
electron correlations.
  [1] M. Nishiyama, Y. Inada, and G.-q. Zheng, Phys. Rev. Lett. 98, 047002 (
2007).
  [2] M. Nishiyama, Y. Inada, and G.-q. Zheng, Phys. Rev. B 71, 220505(R) (2005)
.
联系人：闻海虎 研究员 82649474