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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

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



Contents
Contents

  • General Concept

  • Crystal Structure

  • Pseudogap in High-Tc Superconductor

  • Vortex in High-Tc Superconductor

  • Local Electronic Modulations Observed by STM

  • Summary


Contents1
Contents

  • General Concept

  • Crystal Structure

  • Pseudogap in High-Tc Superconductor

  • Vortex in High-Tc Superconductor

  • Local Electronic Modulations Observed by STM

  • Summary


General concept
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.


General concept1
General Concept

  • Critical Field/Temperature/Current

  • McMillan Limit (PRB. 16,643(1977))


Scanning tunneling spectrum
Scanning Tunneling Spectrum

Rev. Mod. Phys. 79, 353 (2007)


Contents2
Contents

  • General Concept

  • Crystal Structure

  • Pseudogap in High-Tc Superconductor

  • Vortex in High-Tc Superconductor

  • Local Electronic Modulations Observed by STM

  • Summary


Contents3
Contents

  • General Concept

  • Crystal Structure

  • Pseudogap in High-Tc Superconductor

  • Vortex in High-Tc Superconductor

  • Local Electronic Modulations Observed by STM

  • Summary


Crystal structure
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)


Stm topography and spectroscopy of a cleaved bi 2 sr 2 cacu 2 o 8 thin film
STM Topography and Spectroscopy of a cleaved Bi2Sr2CaCu2O8 thin film

Rev. Mod. Phys. 79, 353 (2007)


Contents4
Contents

  • General Concept

  • Crystal Structure

  • Pseudogap in High-Tc Superconductor

  • Vortex in High-Tc Superconductor

  • Local Electronic Modulations Observed by STM

  • Summary


Contents5
Contents

  • General Concept

  • Crystal Structure

  • Pseudogap in High-Tc Superconductor

  • Vortex in High-Tc Superconductor

  • Local Electronic Modulations Observed by STM

  • Summary


From conventional sc to high t c sc
From Conventional SC to High-Tc SC

Rev. Mod. Phys. 79, 353 (2007)


Pseudogap on different sc materials
Pseudogap on different SC Materials

Rev. Mod. Phys. 79, 353 (2007)


Conflicts from y123 nd123
Conflicts from Y123 &Nd123

Rev. Mod. Phys. 79, 353 (2007)


Two scenarios of the mechanism
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)


Recently research
Recently Research

02 June 2013

Nature Physics 9, 442–446 (2013)


Contents6
Contents

  • General Concept

  • Crystal Structure

  • Pseudogap in High-Tc Superconductor

  • Vortex in High-Tc Superconductor

  • Local Electronic Modulations Observed by STM

  • Summary


Contents7
Contents

  • General Concept

  • Crystal Structure

  • Pseudogap in High-Tc Superconductor

  • Vortex in High-Tc Superconductor

  • Local Electronic Modulations Observed by STM

  • Summary


Vortex in high t c superconductor
Vortex in High-TcSuperconductor


Vortex measurement
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)


Difference between 2 kind of sc
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)


Difference between 2 kind of sc1
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)


Contents8
Contents

  • General Concept

  • Crystal Structure

  • Pseudogap in High-Tc Superconductor

  • Vortex in High-Tc Superconductor

  • Local Electronic Modulations Observed by STM

  • Summary


Contents9
Contents

  • General Concept

  • Crystal Structure

  • Pseudogap in High-Tc Superconductor

  • Vortex in High-Tc Superconductor

  • Local Electronic Modulations Observed by STM

  • Summary


Local electronic modulations
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.


The experiment about periodic modulations
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.


Quasiparticle interference oscillations in the superconducting state
Quasiparticle Interference Oscillations In the Superconducting State

Rev. Mod. Phys. 79, 353 (2007)


Quasiparticle interference oscillations in the superconducting state1
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)


Recently research1
Recently Research Superconducting State

Nature 462, 335-338 (2009)


Recently research2
Recently Research Superconducting State

Nature 462, 335-338 (2009)


Contents10
Contents Superconducting State

  • General Concept

  • Crystal Structure

  • Pseudogap in High-Tc Superconductor

  • Vortex in High-Tc Superconductor

  • Local Electronic Modulations Observed by STM

  • Summary


Contents11
Contents Superconducting State

  • General Concept

  • Crystal Structure

  • Pseudogap in High-Tc Superconductor

  • Vortex in High-Tc Superconductor

  • Local Electronic Modulations Observed by STM

  • Summary


Summary
Summary Superconducting State

  • General Concept

  • Crystal Structure

  • Pseudogap in High-Tc Superconductor

  • Vortex in High-Tc Superconductor

  • Local Electronic Modulations Observed by STM

  • Summary