Transcript MiaoyinWang_SSP2_talk

Neutron Scattering on
High Transition Temperature
Superconductors
Miaoyin Wang
Solid State Physics II: Presentation II
Apr., 2010 @ UTK
Outline
1. High Tc Superconductor
2. Neutron Scattering
3. Neutron Scattering on
High Tc Superconductor
1. Superconductor
*Resistance = 0 at Tc
*Meissner Effect
Songxue Chi et al., PRL
1. Superconductor
*More Magnetic Field …
1. Superconductor
BCS Theory = Bardeen & Cooper & Schrieffer
2. High-Tc Superconductor
From Wikipedia
2. High-Tc Superconductor
Property:
Structure
S. Chi et al., PRL
Shiliang Li et al., Wuli
Shiliang Li et al., PRB
2. High-Tc Superconductor
Property: Doping & Phase Diagram
3. Neutron Scattering
Neutron:
No Charge
>Go deep into sample – a bulk detector
Spin 1/2
>Nuclear / Magnetic Structure
For Neutron Energy ~ 1meV
Wavelength ~ 0.1-1 nm
3. Neutron Scattering
Neutron Cross-Section
From NCNR Website
3. Neutron Scattering
Neutron Scattering
What we are interested in?
1. Elastic & Inelastic
2. Energy & Momentum
(transfer)
3. Intensity
4. Experiment No.1
Structure and magnetic phase diagram of
CeFeAsO1-xFx and its relation to
high-temperature superconductivity
Jun Zhao et al.,
Nature Materials 7 , 953-959 (2008).
About Experiment
1. Powder Sample CeFeAsO1-xFx
2. Elastic
3. Nuclear / Magnetic Bragg peak
4. Experiment No.1
About Instrument:
Powder Diffractometry
HB-2A in HFIR, ORNL
4. Experiment No.1
What the data look like…
4. Experiment No.1
What we have found…
Structure distortion
1. Suppressed like AFM
order by doping.
2. Totally disappear in SC
phase.
4. Experiment No.1
What we have found…
4. Experiment No.2
Resonance in the electron-doped high-transitiontemperature superconductor Pr0.88LaCe0.12CuO4-δ
Wilson S D et al., Nature, 2006, 442:59
About Experiment
1. Single Crystal Sample Pr0.88LaCe0.12CuO4-δ
2. Inelastic
3. Spin resonance
4. Experiment No.2
About Instrument:
Triple-axis Spectrometry
ki
Q
kf
BT-2 in NCNR, NIST
4. Experiment No.2
Spin Resonance
4. Experiment No.2
Data
4. Experiment No.2
Result
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.
Thank you!
Thank you!
Thank you!
Thank you!