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NMR study in superconductors

NMR study in superconductors. Kitaoka Lab. M1 Nitta Mariko. Contents. NMR measurement principle of NMR, NMR spectrum Knight shift relaxation rate 1/ T 1 Results of measurement Knight shift 1/ T 1 Summary My work.

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NMR study in superconductors

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  1. NMR study in superconductors • Kitaoka Lab. • M1 Nitta Mariko

  2. Contents • NMR measurement principleof NMR, NMR spectrum Knight shift relaxation rate 1/T1 • Results of measurement Knight shift 1/ T1 • Summary • My work

  3. NMR (Nuclear Magnetic Resonance)measurement NMR Intensity Ex. I=1/2 (Fe) ω= gH0 m=-1/2 I=1/2 gℏ H0 H m=+1/2 I H0＝0 H0≠0 Zeemann splitting e Zeemann interaction Em=-gℏH0m HZeemann= -gℏI・H0

  4. Knight shift NMR Intensity I H e ・Orbital angular momentum(H0rb) ・Magnetic dipole interaction (Hdip) ・Fermi contact interaction(HF) ・Inner core polarization interaction (Hcp) HZeemann = -gℏI・(H0+⊿H) ⊿H = Horb+ Hdip + HF+ Hcp

  5. ω= g (Hres+⊿H) = g Hres(1+K) Knight shift NMR Intensity I H e γ：gyromagnetic ratio Knight shift

  6. What can we know from Knight shift ?~Symmetry of Cooper pair~ K (T) = Ks(T) +Korb Constant Ks (T)~ A χS(T)(spin susceptibility) Tc Spin triplet Sr2RuO4 Tc Spin singlet Al Ks/Kn Ks S=1 S=0 Sr2RuO4: Ishida et al.(1998) UPt3 : Tou et al (1996) L. Fine et al. (1969 ) T/Tc T

  7. What can we know from Knight shift ?~Symmetry of Cooper pair~ Cooper pairing state S=0 orbital part spin part even function (s, d wave) Φ(-(r1-r2)) =Φ(r1-r2) spin-singlet s (s2,s1) = -s (s1,s2) S=1 s-wave d-wave odd function (p wave) Φ(-(r1-r2)) = －Φ(r1-r2) spin-triplet s (s2,s1) = s(s1,s2) ψ(r1-r2;s1,s2) = Φ(r1-r2) σ(s1,s2) p-wave orbital spin

  8. Excitation energy Release the energy Relaxation rate 1/T1 What isT1?? T1 ~ spin-lattice relaxation time I=-1/2 I=+1/2 nuclear spin electronic spin spin-lattice interaction Energy- transfer Time constant T1 1/T1 measurement is a good probe for electronic states !

  9. 1/T1 in various superconductors unconventional superconductors (non BCS) NS(E) NS(E) Point nodes Line nodes N0 N0 EF EF +Δ0 EF +Δ0 EF EF +Δ0 d-wave p-wave EF Conventional type (BCS) s-wave

  10. Summary NMR study Knight shift Cooper pair symmetry or Spin triplet Relaxation time 1/T1 Superconducting gap structure Spin singlet S=1 S=0 or BCS unconventional type Superconducting mechanism

  11. My work Fe-pnictide superconductor “11 series” “122 series” FeSe BaFe2As2 FeSelayer “1111 series” LaFeAs(O,F) FeAslayer FeAslayer Tc max= 8 K Tc max= 38 K F.C.Hsu et al.(2008) Tc max= 55 K M. Rotter et al.(2008)

  12. My work compare 1/T1 in1111,122,11system “La1111” “Ba122” “11” 57Fe- NMR 75As-NQR ~T5 ~T3 ~T3 unconventional superconductor

  13. My workLa1111 system ~s(+-)wave~ S(+-)wave a=4.0208Å OPT Tc=28 K OPT : Tc =28 [K] Heavily-OVD : Tc =5 [K] 75As-NQR experiment H-OVD Tc=5 K

  14. My workLa1111 system ~s(+-)wave~ OPT Hole electron εF ky a=4.0208Å Ｍ E Full gap Full gap kx k electron hole

  15. My workLa1111 system ~s(+-)wave~ H-OVD electron Hole εF ky a=4.0208Å Ｍ E Full gap Full gap kx k electron hole

  16. Future work “1111 series” LaFeAs(O,F) FeAslayer ? Fermi surface in Superconductivity Tc

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