magnetic states of lightly hole- doped cuprates in the clean limit as seen via zero-field muon spin...
TRANSCRIPT
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)
Contents
• IntroductionHigh-Tc cuprate superconductors
• Measurementmuon spin rotation (μSR)
• ResultPhase diagram of YBa2Cu3O6+y
• Conclusion
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
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+
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
sample
YBa2Cu3O6+y for various oxygen-content y
various hole density h
CuO-chain
CuO2 plane
CuO2 plane
hole density
• 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
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
Sμ
detected!!
• The positron emission in the muon decay is asymmetric.
many muons
• Eech muon has different life.
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.
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
Activation temperature TAResult
TA
hole dependence of TA
extrapolation of the m(h,T) power-law
hole dopinghole doping
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!!
hole spin
Holes in CuO2 layer…
Holes are localized.Spins are freezing. Holes are delocalized.
• 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