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Kitaoka Laboratory Nobukatsu Tamura

1/14. Evidence for a Novel Pairing State in Noncentrosymmetric Superconductor CePt 3 Si: A 29 Si-NMR Knight Shift Study. Ref. M. Yogi et al. , J. Phys. Chem. Solids 67 (2006). E. Bauer et al. , Phys. Rev. Lett. 92 , 027003 (2004).

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Kitaoka Laboratory Nobukatsu Tamura

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  1. 1/14 Evidence for a Novel Pairing State in Noncentrosymmetric Superconductor CePt3Si:A 29Si-NMR Knight Shift Study • Ref. • M. Yogi et al., J. Phys. Chem. Solids 67 (2006). • E. Bauer et al., Phys. Rev. Lett. 92, 027003 (2004). • T. Yasuda et al., J. Phys. Soc. Jpn. 73, 1657 (2004). Kitaoka Laboratory Nobukatsu Tamura

  2. Contents 2/14 ・Introduction The lack of inversion symmetry The formation of Cooper-pairs ・Experimental Methods NMR measurement Knight shift ・Experimental Results ・Summary and Future work

  3. The lack of inversion symmetry 3/14 Mirror Not match up !!

  4. Introduction　～ CePt3Si ～ CePt3Si 4/14 The crystal structure c Not match up ab CePt3Si has the crystal structure with lack of inversion symmetry.

  5. Introduction　～ the formation of Cooper-pairs ～ 5/14 Cooper-pair s-wave type Superconductivity is caused by the formation of Cooper-pairs.

  6. Introduction orbital part spin part even function Φ(-(r1-r2)) =Φ(r1-r2) spin-singlet F(s2,s1) = －F(s1,s2) s-wave d-wave odd function Φ(-(r1-r2)) = －Φ(r1-r2) spin-triplet F(s2,s1) = F(s1,s2) p-wave 6/14 Wave function of Cooper pair ψ(r1-r2;s1,s2) = Φ(r1-r2) F(s1,s2) orbital spin

  7. Introduction s-wave d-wave mixture-state p-wave 7/14 Symmetric Non symmetric mixture of spin-singlet and spin-triplet Cooper pair spin-singletor spin-triplet wave function Cooper Pair has mixture state spin singlet + spin triplet Investigatethat by NMR !!

  8. － ⊿E = hγH0 = hω ⊿E = hγ(H0 + Hint) = h (ω+⊿ω) NMR~Nuclear Magnetic Resonance~ 8/14 I = 1/2 H = H0 +Hint Hint H0 Knight shift ＋ ω+⊿ω =γH =γ (H0+Hint) ω=γH0 K ±1/2 -1/2 ω Energy ω+⊿ω ω ⊿ω +1/2 Zeeman splitting K = ⊿ω / ω

  9. Knight shift 9/14 K = ⊿ω / ω K ω ⊿ω ω spin-singlet spin-triplet Al Sr2RuO4 K= 0 (T<<TC) K doesn’t decrease below Tc . K decreases below Tc .

  10. Magnetic order( T < TN ) 10/14 TN< T T < TN Tc TN T <TN ⇒ Magnetic order T. Yasuda et al., J. Phys. Soc. Jpn. 73, 1657 (2004).

  11. 29Si-NMR spectrum 11/14 TN< T T = 4.2 K H0 = 2.0012T 0 T = 0.142 K T < TN H0 = 2.0061T 0 M. Yogi et al., J. Phys. Chem. Solids 67 (2006).

  12. 29Si-NMR spectrum (T < TN) 0 T = 0.142 K H0 = 2.0061T 0 Si 12/14 ω =γ H H = H0 +Hint H0 powder M. Yogi et al., J. Phys. Chem. Solids 67 (2006).

  13. (ω=γH0) 29Si-NMRspectrum Knight Shift T < Tc 13/14 Tc< T T < Tc M. Yogi et al., J. Phys. Chem. Solids 67 (2006). K doesn’t decrease below Tc . The Cooper pair of this SC is dominant spin-triplet.

  14. Summary 14/14 • CePt3Si is theoretically expected that the lack of inversion symmetry gives rise to a mixture of spin-singlet and spin-triplet Cooper pair. • Knight shift doesn’t decrease below Tc at 2T. • It suggests that the Cooper pair of CePt3Si is dominated by spin-triplet component. Future work • Knight shift measurement is necessary under low magnetic fields. • Use single crystal sample without disorder.

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