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Pressure effect on the superconductivity of HgBa2Ca2Cu3O8+
2010.11.17
Shimizu Lab. M1 KAMADA Yukihiro
Contents
• Introduction– The world record of the Tc
– Pressure effect on HgBa2Ca2Cu3O8+ (previous work)– Tc depends on…– Motivation
• Experiment– About diamond-anvil cell (DAC)– High purity of the samples– The amount of the doping carriers– Method of measuring electrical resistance under high pressure with DAC– Method of cooling & determination of the pressure– Experimental result– Discussion
• Summary
The world record of the Tc
Introduction
Tc = 164 K @ 31 GPa
World record of high-Tc!
※ Superconductivity ・ Electrical resistance is Zero ・ Meissner effect
(perfect diamagnetism)
Its superconductivity can’t be explained with BCS theory.
The mechanism of superconductivity still has many mysteries.
Pressure effect on HgBa2Ca2Cu3O8+ (previous work)
The electrical resistivity of Hg-1223 under high pressure
Pressure dependence of the Tc of Hg-series cuprate
L. Gao et al., Phys. Rev. B 50, 4260 (1994)
Introduction
SCAFM AFM
quasi-gap
SC
under dope over dope
optimal dopeoptimal dopeTemperature
00.15 0.15 ～0.20electron hole
Tc depends on…
>0, supplying holes into the CuO2 layers
HgBa2Cam-1CumO2m+2+
m = 3 is the best for high-Tc @ ambient pressure.
aa
c
The carrier concentration
Pressure effect is not only changing lattice constant but also changing hole distribution between CuO2 layers etc…
Introduction
Tc depends on…
F.Nakamura, J.Hori, T.Goko, Y.Uno, N.Kikugawa and T.Fujita, Journal of Low Temperature Physics, Vol. 117. Nos. 5/6, 1999
Xiao-Jia Chen, Viktor V. Struzhkin, Yong Yu, Alexander F. Goncharov, Cheng-Tian Lin, Ho-kwang Mao & Russell J. Hemley, Nature 466, (2010) 950–953
La2-xSrxCuO4 Bi2Sr2Ca2Cu3O10+
Introduction
Motivation
• Try to make a new world record!– High purity of the sample– The amount of the doping carriers– To control the pressure condition– Higher pressure– And so on…
Introduction
About diamond-anvil cell (DAC)
gasket
pressuremedium
sample
Diamond Anvil Cell(DAC)
6 cm
3 cmdiamond
diamond
To explain easily, this picture is the DAC which keeps the pressure by screw.In this experiment, I used the DAC which apply the pressure by gas-pressure system.
※
Experiment
SCAFM
quasi-gap
SC
under dope over dope
optimal dopeoptimal dopeTemperature
00.15 0.15 ～ 0.20electron hole
High purity of the samples
• Sample 1 (S1) & Sample 2 (S2)
– Purity (Hg-1223 : 90%~)
• Sample 1 (S1) : Tc = 134 K @ ambient pressure
– To control a little under doped (annealing in a vacuum)
• Sample 2 (S2) : Tc = 130 K @ ambient pressure
– Not to control doping carriers
Experiment
The amount of the doping carriers
To control the pressure condition
• Sample 2 (S2)– Hydrostatic
• With pressure medium (NaCl)
– Non-hydrostatic• Without pressure medium
Experiment
Method of measuring electrical resistance under high pressure with DAC
Gasket(SUS310S)
Electrical probe (Pt foil)
Pressure Medium(NaCl)
sample
Pressure marker (Ruby chip)
Insulator(c-BN powder + epoxy)
Electrical probe(Au wire)
300 m100 m
1.8 GPa
Sample 2
Hydrostatic (with NaCl) (Sample 1, Sample 2)
※ with microscope.
AC four probe method ※ S1:pserud four probe method
Experiment
Method of measuring electrical resistance under high pressure with DAC
Gasket(SUS310S)
Electrical probe (Pt foil)
sample
Pressure marker (Ruby chip)
Insulator(c-BN powder + epoxy)
300 m
Non-hydrostatic (without pressure medium) (Sample 2)
Sample 2 100 m
0.85 GPa
※ with microscope.
AC four probe method
Experiment
Method of cooling & determination of the pressure
Low temperature generator : Pulse Tube refrigerator (low vibration)
Gas type DAC
different type
Gas type DAC can change the pressure at low temperature.(DAC in the refrigerator)
Measured with PC
CameraPressure determination:• Ruby fluorescence method• Raman shift of diamond
Experiment
Experimental result
Hg-1223 (S1) with NaCl
Hg-1223 (S2) with NaCl
Experiment
Hydrostatic (with NaCl) (Sample 1, Sample 2)
Experimental result
Hg-1223 (S2) with no pressure medium
Tco
Tc
Hg-1223 (S1) at 0.7 GPa
The Tc was defined by same method of the world record
Definition of the Tc
Experiment
Non-hydrostatic (without pressure medium) (Sample 2)
Experimental result
Pressure dependence of Tc about Sample 1 (carrier controlled) and Sample 2 (non-controlled)
Hg-1223 (S1 and S2) with NaCl
The pressure effect of the Tc depends on the sample
Experiment
Experimental result
Pressure dependence of Tc with pressure medium and without pressure medium about Sample 2
?
The pressure effect of the Tc depends on the way how to apply the pressure
Hg-1223 (S2)
Experiment
Discussion
L. Gao et al., Phys. Rev. B 50, 4260 (1994)
Comparing the previous work to my work
Hg-1223 (S1 and S2) with NaCl
Carrier density?But, can’t find any clear reasons.
Discussion
Phase transition?
The change of the Tc by applying the pressure is not continuous
The other discussion…
Hg-1223 (S1 and S2) with NaCl
Summary
• From this experiment– Can’t make the new world record…– Phase transition?
• Future– 1. Higher pressure– 2. X-ray diffraction measurement– 3. Uniaxial pressure– 4. Best condition of the pressure
The new world record of the Tc!?
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