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Transcript Mコロ前期

Pressure effect on high-Tc
cuprate superconductors
2010.06.16
Shimizu Lab. M1 KAMADA Yukihiro
Contents

Introduction
•
•
•
•

About our group
What’s pressure?
Pressure effect on physical properties
Motivation for high-Tc
Experiment
• About Diamond Anvil Cell (DAC)
• My experiment

Summary
Introduction
About our group
Multiple extreme conditions
Over 200 GPa
High Pressure
~ 14 T
Strong Magnetic Field
Today’s main theme!
Low Temperature
~ 15 mK
Introduction
What’s pressure?
Changing physical properties
630 hPa (0.65 気圧)
=63,000 Pa
1,013 hPa (1 気圧)
=101,300 Pa
1 GPa = pressure @ trench × 10
= pressure @ surface × 10,000
= 1 万気圧
surface
200 m
h
k
M
G
2 MPa (20 気圧)
=2,000,000 Pa
continental shelf
: 102
: 103
: 106
: 109
10,000 m
350 GPa (350 万気圧)
trench
0.1 GPa (1000 気圧)
=100,000,000 Pa
Introduction
Pressure effect on physical
properties
※ Superconductivity
・ Electrical resistance is Zero
・ Meissner effect (perfect diamagnetism)
pressure
Able to change physical properties
・ Changing superconducting
transition temperature (Tc)
・ etc…
Kamerlingh Onnes, H., "The Superconductivity of Mercury."
Comm. Phys. Lab. Univ. Leiden; Nos. 122 and 124, 1911.
Introduction
Motivation for high-Tc
History of superconducting transition temperature (Tc)
World record of high-Tc!
Tc = 164 K @ 31 GPa
L. Gao et al., Phys. Rev. B 50, 4260 (1994)
Introduction
Motivation for high-Tc
HgBa2Cam-1CumO2m+2+d
m = 3 is the best for high-Tc!
My experiment
d>0, supplying
holes into the
CuO2 layers
Why? (not clear yet)
c
If we understand these reasons,
we can make clear high-Tc system
and realize higher Tc than now.
a
a
日本大学文理学部 マテリアルサイエンスにおける超高圧技術と高温超伝導研究 高橋 博樹 著 P.119
Introduction
Motivation for high-Tc
World record’s sample
Not the best purity
 Not optimum dope under pressure

→ Sample with purity and optimum dope
under pressure will be able to record
higher Tc?
Try to make a new world record!
Experiment
About Diamond Anvil Cell (DAC)
3 cm
diamond
gasket
pressure
medium
sample
6 cm
diamond
Diamond Anvil Cell
(DAC)
・culet (tip) size:
50 mm~1000 mm (1 mm)
・natural diamond
・synthetic diamond
Merit:
visible → X-ray
small → set refrigerator
Demerit:
cannot use big samples
~ 350 GPa
(≒ the center of the earth)
Experiment
My experiment
Sample
sample
(high purity and under dope)
1.0 GPa
Au wire
Pt wire
NaCl
70 mm
SUS310S
150 mm
300 mm
c-BN + epoxy
ruby
(pressure marker)
300 mm
Highest Tc = 150 K @ 13 GPa
Cooling with refrigerator and
measuring electrical resistance
Applying more pressure
Sorry, but I’ll show you details on
next semester’s presentation.
Summary



Pressure is very interesting method for changing physical
properties.
DAC is very useful for applying high pressure.
My experiments
• Measuring about Hg-1223’s pressure dependence of Tc
• Highest Tc = 150 K @ 13 GPa
Future
→ More experiments
→ New world record
→ Making clear high-Tc system about cuprate
→ Superconductivity @ room temperature
pressure
pleasure
End
Thank you for your attention!