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High-T c Superconductor Surface State

High-T c Superconductor Surface State. Group member: 陈玉琴、郭亚光、贾晓萌、刘俊义、刘晓雪 　彭星星、王建力、王鹏捷 ★ 、喻佳兵 ★ :Group Leader & Speaker. Foreword. Contents. General Concept Crystal Structure Pseudogap in High-T c Superconductor Vortex in High-T c Superconductor

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High-T c Superconductor Surface State

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  1. High-Tc Superconductor Surface State Group member: 陈玉琴、郭亚光、贾晓萌、刘俊义、刘晓雪 　彭星星、王建力、王鹏捷★、喻佳兵 ★:Group Leader & Speaker

  2. Foreword

  3. Contents • General Concept • Crystal Structure • Pseudogap in High-Tc Superconductor • Vortex in High-Tc Superconductor • Local Electronic Modulations Observed by STM • Summary

  4. Contents • General Concept • Crystal Structure • Pseudogap in High-Tc Superconductor • Vortex in High-Tc Superconductor • Local Electronic Modulations Observed by STM • Summary

  5. General Concept • Disappearance of Resistance (H.K.Onnes,Commun.Phys.Lab.12,120(1911) • Meissner Effect (Meissner, W, Naturwissenschaften 21 (44): 787–88.(1933) • BCS Theory (Physical Review 97 (6): 1724–1725.) Two electrons with opposite spin and momentum combine a Cooper pair, the coherence length is about 10-4cm which can be unimpeded form current. • Energygap In order to break a pair, one has to change energies of all other pairs. This means there is an energy gap for single-particle excitation, unlike in the normal metal.

  6. General Concept • Critical Field/Temperature/Current • McMillan Limit (PRB. 16,643(1977))

  7. Scanning Tunneling Spectrum Rev. Mod. Phys. 79, 353 (2007)

  8. Contents • General Concept • Crystal Structure • Pseudogap in High-Tc Superconductor • Vortex in High-Tc Superconductor • Local Electronic Modulations Observed by STM • Summary

  9. Contents • General Concept • Crystal Structure • Pseudogap in High-Tc Superconductor • Vortex in High-Tc Superconductor • Local Electronic Modulations Observed by STM • Summary

  10. Crystal Structure Fig.(a) Bi2Sr2CaCu2O8 Fig.(b) YBa2Cu3O6 Fig.(c) Schematics of the dx2−y2superconducting gap in the unit-cell coordinate system. Rev. Mod. Phys. 79, 353 (2007)

  11. STM Topography and Spectroscopy of a cleaved Bi2Sr2CaCu2O8 thin film Rev. Mod. Phys. 79, 353 (2007)

  12. Contents • General Concept • Crystal Structure • Pseudogap in High-Tc Superconductor • Vortex in High-Tc Superconductor • Local Electronic Modulations Observed by STM • Summary

  13. Contents • General Concept • Crystal Structure • Pseudogap in High-Tc Superconductor • Vortex in High-Tc Superconductor • Local Electronic Modulations Observed by STM • Summary

  14. From Conventional SC to High-Tc SC Rev. Mod. Phys. 79, 353 (2007)

  15. Pseudogap on different SC Materials Rev. Mod. Phys. 79, 353 (2007)

  16. Conflicts from Y123 &Nd123 Rev. Mod. Phys. 79, 353 (2007)

  17. Two Scenarios of the Mechanism • 1. The scenario of preformed pairs.(Fig. (a)) • 2. The scenario of a non-superconducting related pseudogap. (Fig. (b)) Rev. Mod. Phys. 79, 353 (2007)

  18. Recently Research 02 June 2013 Nature Physics 9, 442–446 (2013)

  19. Contents • General Concept • Crystal Structure • Pseudogap in High-Tc Superconductor • Vortex in High-Tc Superconductor • Local Electronic Modulations Observed by STM • Summary

  20. Contents • General Concept • Crystal Structure • Pseudogap in High-Tc Superconductor • Vortex in High-Tc Superconductor • Local Electronic Modulations Observed by STM • Summary

  21. Vortex in High-TcSuperconductor

  22. Vortex Measurement Illustration of the vortex-lattice imaging by STM: (a) Local SIN junction with typical BCS s-wave characteristics when the tip is between vortices. (b) Local NIN junction with a constant conductance for a dirty BCS superconductor when the tip is positioned over a vortex core. Rev. Mod. Phys. 79, 353 (2007)

  23. Difference between 2 kind of SC Conventional Superconductor High-Tc Superconductor Left: Phys. Rev. Lett. 62, 214 (1989) Right: Rev. Mod. Phys. 79, 353 (2007)

  24. Difference between 2 kind of SC Conventional Superconductor High-Tc Superconductor Left: Phys. Rev. Lett. 62, 214 (1989) Right: Rev. Mod. Phys. 79, 353 (2007)

  25. Contents • General Concept • Crystal Structure • Pseudogap in High-Tc Superconductor • Vortex in High-Tc Superconductor • Local Electronic Modulations Observed by STM • Summary

  26. Contents • General Concept • Crystal Structure • Pseudogap in High-Tc Superconductor • Vortex in High-Tc Superconductor • Local Electronic Modulations Observed by STM • Summary

  27. Local Electronic Modulations Two different types of spatial variations have been seen by STS: Large but irregular spatial variations of the gap, with typical lengths scales of the order of 3–10 nm, in samples which are not specially treated for homogeneity; Weaker but spatially periodic LDOS modulations with a wavelength of about 1.6–2 nm.

  28. The Experiment about Periodic Modulations • 1.The first indication of the presence of such periodic spatial modulations was the observation that around the center of a vortex there is a modulation of the LDOS. • 2. Subsequently, Howald, Eisaki, Kaneko, Greven,and Kapitulnik 2003 found that charge modulations were also present in the absence of a magnetic field. • They reported that the structure appeared at an energy around 25 meV and that the superperiod did not disperse with energy. • 3. Hoffman, McElroy, et al. 2002 reported similar zero-field electronic modulations, but in contrast to Howald, Eisaki, Kaneko, Greven, and Kapitulnik • 2003 they found that these modulations disperse with energy,energy. They successfully interpreted their findings in terms of quasiparticle interference due to scattering from impurities and other inhomogeneities. • 4.More recently Vershinin, Misra, Ono, et al. 2004 observed electronic modulations in the pseudogap phase above T.

  29. Quasiparticle Interference Oscillations In the Superconducting State Rev. Mod. Phys. 79, 353 (2007)

  30. Quasiparticle Interference Oscillations In the Superconducting State Representation of the quasiparticle energy along the Fermi surface. qAand qBare two possible vectors connecting quasiparticle states with identical energies, giving rise to interference patterns. Science 279, 353 (2007)

  31. Recently Research Nature 462, 335-338 (2009)

  32. Recently Research Nature 462, 335-338 (2009)

  33. Contents • General Concept • Crystal Structure • Pseudogap in High-Tc Superconductor • Vortex in High-Tc Superconductor • Local Electronic Modulations Observed by STM • Summary

  34. Contents • General Concept • Crystal Structure • Pseudogap in High-Tc Superconductor • Vortex in High-Tc Superconductor • Local Electronic Modulations Observed by STM • Summary

  35. Summary • General Concept • Crystal Structure • Pseudogap in High-Tc Superconductor • Vortex in High-Tc Superconductor • Local Electronic Modulations Observed by STM • Summary

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