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!?