Kitaoka Lab Kaneda Takuya

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Magnetic states of lightly hole-doped cuprates in the clean limit as seen via zero- field muon spin spectroscopy Kitaoka Lab Kaneda Takuya F. Coneri, S. Sanna, K. Zheng, J. Lord, and R. De Renzi, Phy. Rev. B 81, 104507 (2010)

description

Magnetic states of lightly hole-doped cuprates in the clean limit as seen via zero-field muon spin spectroscopy. F. Coneri, S. Sanna, K. Zheng, J. Lord, and R. De Renzi, Phy. Rev. B 81 , 104507 (2010). Kitaoka Lab Kaneda Takuya. Contents. Introduction High- T c cuprate superconductors - PowerPoint PPT Presentation

Transcript of Kitaoka Lab Kaneda Takuya

Page 1: Kitaoka Lab Kaneda Takuya

Magnetic states of lightly hole-doped cuprates in the clean limit as

seen via zero-field muon spin spectroscopy

Kitaoka LabKaneda Takuya

F. Coneri, S. Sanna, K. Zheng, J. Lord, and R. De Renzi, Phy. Rev. B 81, 104507 (2010)

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Contents

• IntroductionHigh-Tc cuprate superconductors

• Measurementmuon spin rotation (μSR)

• ResultPhase diagram of YBa2Cu3O6+y

• Conclusion

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1910 19900

60

80

100

160

LaSrCuO

YBaCuO

BiCaSrCuO

TlCaBaCuOHgCaBaCuOTlCaBaCuO

HgCaBaCuO( under high pressur

e )

HgCaBaCuO( under high pressure )

NbNbC

V3SiNbN

Nb3SnPb

Nb3Ge

Nb-Al-Ge

liquid nitrogen

Hg

1911 1986

0

100

160

LaBaCuO

Tc (K)

(year)

Increase of Transition Temperature (Tc)

Cuprate Superconductor

High-Tc Cuprate Superconductors Introduction

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crystal structureof La-Ba-Cu-O

La3+2-xBa2+

xCuO4

Cu2+x

CuO2 面

電荷供給層

電荷供給層

La (Ba)

electric conductivity with hole doping

Superconductivity emerges with optimal doping.

Cu

O

La(Ba)

High-Tc Cuprate Superconductors Introduction

charge reservoir

CuO2 layer

charge reservoir

La2CuO4

d(x2-y2)

Cu+2

(3d9)

3d(x2-y2)Cu(3d104s1)

3d(3z2-r2)

3d(xy)

3d(yz, zx)

La3+→Ba2+

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In order to understand the ground state of cuprate superconductor, careful study about its underdoped region is required.

High-Tc Cuprate Superconductors Introduction

AFM

SCSC

AFM

charge reservoir

CuO2 layer

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sample

YBa2Cu3O6+y for various oxygen-content y

various hole density h

CuO-chain

CuO2 plane

CuO2 plane

hole density

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• spin: I = ½• gyromagnetic ratio: 135.53MHz/T

• mean lifetime: 2.2μs

What is μSR (muon spin rotation) ? Measurement

Property of Muon

It’s very sensitive even to low magnetic field.

pion mean lifetime: 26ns

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sample

internal field

positron counter

muon (μ+)

positron

• Internal field

about t μs later…

Internal field is determined from time dependence of muon asymmetry.

What is μSR (muon spin rotation) ? Measurement

H

detected!!

• The positron emission in the muon decay is asymmetric.

many muons

• Eech muon has different life.

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μSR Result Result

h=0.02

h=0.04

h=0.07

hole density

only depend on muon’s life

damped oscillationstatic field

Internal field is not static.

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TN

hole density

• TN drop rapidly with increasing the hole density h.

• For h =0.035, m(h,T) deviates from power-law behavior (dashed line) and an upturn (solid line) appears.

)0(

,, 2

AOB

ThBThm AO

D

m :magnetizationh :hole densityBAO :internal field at the apical oxygen

Temperature dependence of the moment Result

Thermally activated regime (high temperature) & Re-entrant regime (low temperature)

Thermally activated

Re-entrant

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Activation temperature TAResult

TA

hole dependence of TA

extrapolation of the m(h,T) power-law

hole dopinghole doping

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Phase diagram Result

AFM

SCRe-entrant

Thermallyactivated

• Re-entrant regime Holes are localized.

Spins are freezing.

The moment recovers to 0.6μB.

• Thermally activated regimeHoles are delocalized.

AFM phase is separeted into two regimes.

AFM phase vanishes atSC phase emerges at

QCP!!

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hole spin

Holes in CuO2 layer…

Holes are localized.Spins are freezing. Holes are delocalized.

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• There are two distinct regimes in AFM phase.

• In re-entrant regime holes are localized and spins are freezing.

• The critical hole density hc and hs have the same value. And the value h = 0.056 is a quantum critical point (QCP) for the cuprate clean limit.

Conclusion

Re-entrant and Thermally Activated