1 / 24

Satoshi Furukawa

Fe-pnictide high T c Superconductors. Satoshi Furukawa. Contents. ・ History of Superconductivity ・ Compare Fe- pnictide system to High- T c cuprate ・ Fe-pnictide Superconductor (La1111 series) career doping

leanna
Download Presentation

Satoshi Furukawa

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Fe-pnictide high Tc Superconductors Satoshi Furukawa

  2. Contents ・ History of Superconductivity ・ Compare Fe-pnictide system to High-Tc cuprate ・ Fe-pnictide Superconductor (La1111 series) career doping effect of pressure effect of elemental substitution hydrogen doping crystal structure ・ Summery and future work

  3. History of Superconductivity 1900 1920 1940 1960 1980 2000 2020 Year 200 metal heavy fermion system Discovery of superconducting phenomenon high-Tc cuprate 163 Hg-Ba-Ca-Cu-O 1911 iron-based system under high pressure （ ） 150 Hg-Ba-Ca-Cu-O Tl-Ba-Ca-Cu-O Bi-Sr-Ca-Cu-O Heavy fermion superconductor 100 Transition temperature (K) 1986 1979 Y-Ba-Cu-O 77 SmO F FeAs 50 0.9 0.11 MgB2 High-Tc cuprate superconductor La-Ba-Cu-O LaO F FeAs PuCoGa5 Nb Ge 0.11 0.89 Nb Pb CeCu2Si2 NbN LaOFeP Hg NbC 0 2006 Iron-based high-Tc superconductor

  4. Fe- pnictide Superconducting family “1111 system” “122 system” “111 system” “11 system” LaFeAsO1-y BaFe2As2 LiFeAs FeSe FeSelayer FeAslayer FeAslayer FeAslayer Tc max= 55 K Tc max= 38 K Tc max= 18 K Tc max= 8 K M. Rotter et al.(2008) X.C.Wang et al.(2008) F.C.Hsu et al.(2008)

  5. High-Tccuprate La Cu O Sr2+ La2-xSrxCuO4 charge reservoir lay Cu+2 (3d9) Hole dope (La3+ → Sr2+)

  6. Fe- pnictide Superconductor LaFeAsO1-xFx Fe+3 charge reservoir lay (3d6) e- AFM F Electron dope (O2- → F-)

  7. Comparison -Phase diagram and doping mechanism- La Cu O Sr2+ Fe-pnictidesystem High-Tc cuprate Temperature AFM e- ・ Layered structure (charge reservoir layer & conduction layer) F ・Superconductivity appears by doping carriers. ・Superconducting transition related to a magnetic instability.

  8. What is the originof superconductivity of Fe pnictide ? What is the cause of the Tc enhancement ? ①　career doping ②　crystal structure

  9. Effect of pressure LaFeAsO0.89F0.11 43K pressure 28K La ▲ H. Takahashi et al., Nature 453 (2008) 376 Tcincreases from 28Kto 43K by pressure

  10. Effect of elemental substitution 55K elemental substitution RE REFeAsO1-y La 28K rare earth element ▲ K. Miyazawa et al., J. Phys. Soc. Jpn, 78 (2009) 034712 smaller ion radius

  11. Effect of elemental substitution La 55K Ce Pr Nd Sm Gd Tb Dy Y elemental substitution RE REFeAsO1-y La 28K rare earth element ▲ K. Miyazawa et al., J. Phys. Soc. Jpn, 78 (2009) 034712 Tcincreases from 28Kto 55K by elemental substitution 原子半径 smaller ion radius

  12. Hydrogen doping –LaFeAsO1-yHx Pr(H) Ce(H) ● La1111：27K →La1111(H): 38.5K Ce1111：40K → Ce1111(H): 47.8K Pr1111：48K → Pr1111(H): 51.5K La(H) ● Nd Pr ● Ce La

  13. Crystal structure –Pnictgen height- As Pnictgen height Fe Tc depends on pnictgen height

  14. Crystal structure -α- regular tetrahedron As Fe αis As-Fe-As angle α regular tetrahedron Tc increases Tcis dependent on α

  15. What is the originof superconductivity of Fe pnictide ? ①　antiferromagneticspin fluctuations ②　orbital degeneracy (Fe 3d) ③　fermi surface (Hole andelectron )topology

  16. Summary and future work What is the cause of the Tc enhancement ? ・ career doping ・ crystal structure(pnictgen height and α) What is the originof superconductivity of Fe pnictide ? ・ the antiferromagnetic spin fluctuations ・ orbital degeneracy ・ fermi surface topology My future work is to find the cause what does determines Tc in La1111 system!! LaY1111(Tc=34K), La1111H (Tc=32K )

  17. Thank you for listening

  18. As Fe

  19. Cu O Cu O CuO2 plane La3+2-xSr2+xCuO4 La2CuO4 Cu2+x Cu+2 (3d9) Cu Cu O O t U Antiferromagnetism(AFM) ｔ≪Ｕ　⇒　Mott insulator Superconductivity(SC)

  20. Recovery curve of nuclear magnetization Excitation Thermal equilibrium state M = M（t） Relaxation M = M（∞） M = 0 ~ Appendix ~ Iz =±3/2 After t… Iz =±1/2 M M(t) = M(∞)[1- exp(-3t/T1)] t time

  21. Fe-, As-面間距離の変化 ~ Appendix ~ FeAs4 四面体が正四面体構造に 近づくとき、Tcは最も上昇する !! NdFeAsO0.6 LaFeAsO0.6 As LaFeAsO Fe Fe Fe FeAs4-tetrahedron Fe Neutron diffraction ~ C. H. Lee et al. JPSJ,77(2008)

  22. NQR frequency (75νQ) Vzz: electric field gradient (EFG) at As nuclear site Vzz(EFG) is dominated by two contributions ① Charge distributionaround As atoms (Fe, La,,,,) • Charge distribution • at As(4p)orbitals As • Hybridization between • Fe(3d) and As(4p) orbitals EFG EFG As Fe Fe Fe Fe • Tc is very sensitive to local configuration of Fe & As Fe Fe Fe NdFeAsO1-y LaFeAsO1-y Close to regular tetrahedron Fe C. H. Lee et al., JPSJ (2008)

More Related