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Neutron Scattering on. High Transition Temperature Superconductors Miaoyin Wang Solid State Physics II: Presentation II Apr., 2010 @ UTK. Outline. 1. High T c Superconductor 2. Neutron Scattering 3. Neutron Scattering on High T c Superconductor. 1. Superconductor.

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neutron scattering on

Neutron Scattering on

High Transition Temperature

Superconductors

Miaoyin Wang

Solid State Physics II: Presentation II

Apr., 2010 @ UTK

slide2

Outline

1. High Tc Superconductor2. Neutron Scattering3. Neutron Scattering on High Tc Superconductor

slide3

1. Superconductor

*Resistance = 0 at Tc*Meissner Effect

Tc

Songxue Chi et al., PRL

Transition Temperature

slide4

1. Superconductor

*More Magnetic Field …

H

SC II

SC

Temperature

Tc

slide5

1. Superconductor

BCS Theory = Bardeen & Cooper & Schrieffer

Phonon

="glue"

slide6

2. High-Tc Superconductor

More system to compare

Cu is not so special!

From Wikipedia

slide7

2. High-Tc Superconductor

Property:Structure

Shiliang Li et al., Wuli

S. Chi et al., PRL

Shiliang Li et al., PRB

slide8

2. High-Tc Superconductor

Property: Doping & Phase Diagram

slide9

3. Neutron Scattering

Neutron:

No Charge

>Go deep into sample – a bulk detector

Spin 1/2

>Nuclear / Magnetic Structure

1 GeV

For Neutron Energy ~ 1meVWavelength ~ 0.1-1 nm

slide10

3. Neutron Scattering

Neutron Cross-Section

Neutron Loves H!

Be aware of plastic...

From NCNR Website

slide11

3. Neutron Scattering

Neutron ScatteringWhat we are interested in?1. Elastic & Inelastic2. Energy & Momentum (transfer)3. Intensity

?

slide12

4. Experiment No.1

Structure and magnetic phase diagram of CeFeAsO1-xFx and its relation to high-temperature superconductivityJun Zhao et al., Nature Materials 7 , 953-959 (2008). About Experiment1. Powder Sample CeFeAsO1-xFx2. Elastic3. Nuclear / Magnetic Bragg peak

slide13

4. Experiment No.1

About Instrument: Powder Diffractometry

HB-2A in HFIR, ORNL

slide14

4. Experiment No.1

What the data look like…

slide15

4. Experiment No.1

What we have found…

Structure distortion1. Suppressed like AFM order by doping.2. Totally disappear in SC phase.

slide16

4. Experiment No.1

What we have found…

slide17

4. Experiment No.2

Resonance in the electron-doped high-transition-temperature superconductor Pr0.88LaCe0.12CuO4-δWilson S D et al., Nature, 2006, 442:59 About Experiment1. Single Crystal Sample Pr0.88LaCe0.12CuO4-δ2. Inelastic3. Spin resonance

slide18

4. Experiment No.2

ki

About Instrument: Triple-axis Spectrometry

Q

kf

BT-2 in NCNR, NIST

slide19

4. Experiment No.2

Spin Resonance

slide22

Summary

1.Structure distortion is strongly related to AFM order and superconductivity.2. Structure distortion is suppressed with doping, and vanishes in the SC phase.3. Spin Resonance independence with doping type (hole or electron).4. Resonance energy is always proportional to Tc, which suggests that the resonance is the universal feature in high-Tc superconductor.