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Unusual superconducting and magnetic characteristics in multilayered high-T c cuprates

Unusual superconducting and magnetic characteristics in multilayered high-T c cuprates. < Reference> Unusual magnetic and superconducting characteristics in multilayered high-Tc cuprates : 63 Cu NMR study H.Kotegawa et al., Phys.Rev.B.64.064515(2001)

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Unusual superconducting and magnetic characteristics in multilayered high-T c cuprates

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  1. Unusual superconducting and magnetic characteristics in multilayered high-Tc cuprates <Reference> Unusual magnetic and superconducting characteristics in multilayered high-Tc cuprates : 63Cu NMR study H.Kotegawa et al., Phys.Rev.B.64.064515(2001) Coexistence of superconductivity and antiferromagnetism in multilayered high-TC cuprates : 63Cu NMR study H.Kotegawa et al., Phys.Rev.B.69.014501(2004) Kitaoka Laboratory Machiko Abe cuprate 銅の化合物

  2. NMR measurements Abstract ・Multilayered high-Tｃcuprates include two types of CuO2 planes. ・High temperature superconductivity occurs in these planes. ・ These CuO2 planes are different in hole doping levels. ・ The difference between them is concerned with the unusual superconducting characteristics. Multilayered high-Tｃcuprates 多層型銅酸化物高温超伝導体

  3. Outline • Introduction • History of superconductivity • Structure of multilayered high-Tc cuprates • Experimental data and discussions • 63Cu-NMR • Knight shift(K ) • hole doping level(Nh) • 3. Summary

  4. Resistance(Ω) 1957 BCS theory Temperature(K) Phonon mediated superconductivity. 1957 － － Cooper pair Tc＜～40K in the framework of this theory. History of superconductivity 1911 Kamerlingh Onnes discovered superconductivity. Transition temperature TC (K) 1911 year

  5. History of high-Tc cuprates The highest Tc !!! Hg-based type 160K (under high pressure) (under high pressure) 133K 1993 Transition temperature TC (K) La-based type years year They cannot be explained by BCS theory. 1986

  6. charge-reservoir layer O Cu Crystal structure of Hg-based high-TC cuprates HgBa2Can-1CunOy multilayered high-Tc cuprates CuO2 plane 5 layers (n=5) 4 layers (n=4) Hg 3 layers (n=3) Ba OP (outer plane) 2 layers (n=2) 1 layer (n=1) Ca Cu IP (inner plane) Hg-1201 Hg-1212 Hg-1223 Hg-1234 Hg-1245 charge-reservoir layer 電荷供給層

  7. half-filled eg Cu(3d104s1) O(2p4) dx2-y2 d3z2-r2 Cu 3d Cu2+(3d9) O2-(2p6) t2g dxy dyz, dzx Cu O Cu O antiferromagnetism temperature superconductivity Hole doping level CuO2 plane Antiferromagnetism carrier(hole) doping Superconductivity occurs below TC. Mott insulator Antiferromagnetism 反強磁性

  8. optimallydope underdope overdope Transition temperature antiferromagnetism superconductivity Hole doping level Purpose of the experiment ・ hole doping level ・ the number of CuO2 planes superconductivity

  9. low high Samples used for the experiment n=3 n=4 n=5 doping level doping level ・Cu-1245 ・Hg-1223 ・Cu-1223 ・Hg-1223 ・Cu-1223 ・Hg-1234 ・Cu-1234 ・Cu-1234 low high OP IP OP

  10. Cu: I = Zeeman interaction 63Cu-NMR(Nuclear Magnetic Resonance) Quadrupole interaction nuclear spin Hext The NMR experiment reveals the local information at the IP and OP. electronic spin external magnetic field Quadrupole interaction 電気四重極相互作用

  11. ⊿H H Hres Hext ω=γ(Hres+⊿H) =γHres(1+K) <NMR spectrum> TC 0.6 Kα(T) = Kspin,α(T) + Korb,α (α= ab , c) overdope T-dependent 0.4 (%) s,ab K 0.2 0 0 100 200 300 T (K) Knight shift (K ) ～The rate of the shift～ γ：gyromagnetic ratio ① ② gyromagnetic ratio 磁気回転比

  12. Nh=0.0462+0.502 Kspin,ab(RT) At room temperature total doping level(δ) Nh(OP) Nh(IP) Nh(IP) Nh(OP) the local doping level(Nh) Estimation of local doping levels n=1 or 2 compounds

  13. Hg1234 (Cu,Ni)1234 (Cu,C)1234 (Tc =123K) total doping level(δ) (Tc (Tc =106K) =117K) n=4 low high (%) spin K OP OP TC OP the local doping level TC TC IP IP IP K s,α(OP)＞K s,α(IP) Nh(OP)＞Nh(IP) 0 200 0 200 0 200 Temperature (K) 63Cu Knight shift （spin part）

  14. n=4 ⊿Nｈ n=3 Analysis of experimental data overdope optimallydope underdope （total doping level / number of CuO2 plane） ⊿Nｈincreases as δ or n increases.

  15. ⊿Nｈ≧～0.07 ⊿Nｈ≦～0.07 Cu1234 (Tc=106K) ⊿Nｈ=0.079 Hg1223 (Tc=133K) ⊿Nｈ=0.045 TC OP TC OP Kspin,ab(％) Kspin,ab(％) IP IP 0 200 200 0 Tc2 Tc Tc dK/dT (a.u.) dK/dT (a.u.) 0 200 0 200 A unique Tc for IP and OP different TC for IP and OP dKspin,ab(T)/dT ～To see in detail the T dependence of Ks,ab The highest Tc !!!

  16. superconductivity (below TC=108K) antiferro- magnetism (below TN=60K) superconductivity (below TC=108K) In five-layered compounds・・・ Hg1245 (n=5) ⊿Nｈ becomes much larger and IP becomes heavily underdoped. (⊿Nｈ=0.158) Antiferromagnetic spin correlation develops below～140K Coexistence of superconductivity and antiferromagnetism was found in five-layered compound Hg-1245

  17. Summary ■ ⊿Nｈ is small ■⊿Nｈ is large ■ ⊿Nｈ becomes much larger and IP becomes heavily underdoped・・・ IP and OP act as the same. A unique and high TC IP and OP show different characteristics. different TC for IP and OP Magnetic characteristics develop at IP Antiferromagnetiｓｍ coexists with superconductivity in a unit cell.

  18. + － － － － Force of attraction between two electrons (Cooper pair) Electron-phonon interaction BCS theory (1957) Phonon mediated superconductivity Tc＜～40K in the framework of BCS theory.

  19. superconductivity antiferromagnetic Tc TN transition temparature(K) dx2-y2 pσ Hole concentration (δ/n) Cu O <orbital overlap in CuO2 plane>

  20. ・ ≧ 3) Multilayered high-T cuprate (n c 0.6 OP overdope (%) 0.4 ∝Nｈ(doping level) IP s,ab K 0.2 underdope 0 0 100 200 300 T (K) Knight shift (K ) quasi-particle density of state SC transityion temparature

  21. Hg1234 (Cu,C)1235 (Cu,Ni)1234 (Cu,C)1234 (Tc =123K) (Tc (Tc (Tc =106K) =90K) =117K) Hg1223 (Tc=133K) TC T c (%) OP T OP c spin K IP IP 200 0 200 T c 63Cu Knight shift （spin part） n=3 n=4 n=5 Hg1223 (Tc=115K) (Cu,C)1223 (Tc=119K) (Cu,C)1223 (Tc=71K) 0.6 OP OP T OP OP TC c 0.4 OP TC T c OP s IP T c IP IP 0.2 IP IP IP 0 0 200 0 200 0 0 200 0 200 0 200 0 200 Temperature (K) T>Tc <underdoped> K s,abdecreases with decreasing T. <overdoped> K s,abis nearly T independent.

  22. <assumption> the apical oxygen has the point-charge. Point-charge model Mudelung potential n=3 ∝ ⊿Nｈ doping level (Nh) Hole distribution (theoretical prediction) n=5 n increase ⊿Nｈ δ(total doping level ) increase ⊿Nｈ ⊿Nｈincreases as δ or n increases.

  23. n=3 ⊿Nｈ=0.014 ⊿Nｈ=0.039 ⊿Nｈ=0.045 ⊿Nｈ=0.073 Tc Tc Tc Tc 1 OP IP 0 0 200 0 200 0 200 0 200 dK/dT (a.u.) n=4 n=5 ⊿Nｈ=0.06 ⊿Nｈ=0.079 ⊿Nｈ=0.121 ⊿Nｈ=0.108 Tc2 Tc2 Tc2 Tc Tc Tc Tc 1 0 0 200 0 200 0 200 0 200 Temperature (K) dKs,ab(T)/dT

  24. Superconducting gap

  25. Hg-1245 ZF-NMR

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