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Kitaoka Laboratory

Coexistence of superconductivity and antiferromagnetism in multilayered high- T c superconductor. Kitaoka Laboratory. SHIMIZU SUNAO. H.Kotegawa et al Phys.Rev.B 69,014501(2004). Contents. High – Tc superconductor Antiferromagnetism. Introduction. Knight shift NQR ZF-NMR

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Kitaoka Laboratory

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  1. Coexistence of superconductivity and antiferromagnetism in multilayered high-Tc superconductor Kitaoka Laboratory SHIMIZU SUNAO H.Kotegawa et al Phys.Rev.B 69,014501(2004)

  2. Contents • High – Tc superconductor • Antiferromagnetism Introduction • Knight shift • NQR ZF-NMR • Data and results Experiment Summary

  3. HgCaBaCuO （高圧下） 160 HgCaBaCuO （高圧下） TlCaBaCuO HgCaBaCuO TlCaBaCuO BiCaSrCuO 100 YBaCuO 80 The upper limit of Tc is about 30~40K 60 LaSrCuO Nb3Ge V3Si LaBaCuO NbN NbC Pb Nb-Al-Ge Nb3Sn Nb • 「The limit of BCS」 Hg 0 年 1910 1930 1950 1970 1990 Discovery of the high-Tc superconductivity Tc -100℃ 160 100 liquid nitrogen -273℃ O 1911 1986

  4. High-Tc superconductor CuO2 plane charge reservoir layer A.F. ; antiferromagnetism （電荷供給層） SC ; superconductivity

  5. exchange interaction J Si・Si+1 J: size of interaction Si , Si+1: electron spin REPULSIVE force makes magnetic order. Antiferromagnetism

  6. doping holes (picking out electrons) Metal with antiferrromagnetic property Metal Insulator to metal Insulator

  7. HgBa2Canー１CunO2n+2+δ Highest-Tc Record! OP IP IP* IP OP Hg-1201 Hg-1212 Hg-1223 Hg-1234 Hg-1223 Hg-1245 Hg-1245 Hg-1256 Crystal Structures Hg ~ Hg-based cuprates ~ O Ba Cu Ca

  8. n≧3 ; two types of CuO2 plane Different hole density at OP or IP Cu OP IP O Multilayerd High-Tc superconductor

  9. Hg Ba O OP Ca Cu IP bulk superconductivity ; Tc = 108K IP* IP OP H (T) HgBa2Ca4Cu5O

  10. Hint ∝M M ; magnetic moment Hint I Hint＝ 0 Hint ≠0 f ( MHz) ZFーNMR Antiferromagnetic order ferromagnetic order

  11. IP ; Affected by the internal field antiferromagetic order Hint = ω / γ Hint(IP) = 6.1 T Hint(IP*) = 7.7 T OP ; Nuclear quadrupole resonance perturbed by internal field νQ = 8.37 MHz (IP) 16.05 MHz (OP) Internal field

  12. SC ;Tc = 108 K OP AF; M = 0.3μB IP AF; M = 0.37μB IP* AF; M = 0.3μB IP SC ;Tc = 108 K OP M = 0.64 μB HgBa2Ca4Cu5O La2CuO4

  13. H ＝ 0 H≠0 H Energy=－μ・H =－　　I・H H e H I resonance condition H+H= ω/γ ∴H = ω/γ－　H =ω/γ(1－Ｋ) H= ω ∴H=ω/γ K:Knight shift K H Knight shift

  14. Nh(OP)=0.0462 + 0.502 Kab,spin(RT,OP) δ= {3Nh(IP) + 2Nh(OP)} / 5 δ= 0.12 Nh(IP) ~ 0.06 0.06 0.22 Doping level K = Kspin(T) + Korb Nh(OP) ~0.22

  15. OP IP IP* IP OP summary SC ;Tc = 108 K AF ; M = 0.3μB AF ; M = 0.37μB AF ; M = 0.3μB SC ;Tc = 108 K Nh(OP) ; 0.22 Nh(IP) ; 0.06

  16. ＋ ＋ ＋ ＋ ⅰ) I = 0 m = ±3/2 m = ±1/2 νQ = 8.37 MHz (IP) 16.05 MHz (OP) energy splitting ; I = 3/2 NQR ⅱ) I 　≧ 1 I ; nuclear spin

  17. AM M BM Hint Kspin, α= ( Aα+4B) χspin ( Ac+4B) Kspin, c 0.267 (IP) = = Kspin, ab ( Aab+4B) 0.379(OP) Ac = －170 kOe/μB Aab = 37 kOe/ μB B (IP) = 61 kOe/ μB M (IP) = 0.30 μB {Aab－　4B } = －207 kOe/ μB M (IP*) = 0.37 μB Hint = {Aab－　4B } M

  18. t < U t: kinetic energy U: potential energy Nh(OP) =0.22 Nh(IP) = 0.06

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