Markus Hcker

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What Pins Stripes in La2-xBaxCuO4?
Markus Hücker
Neutron Scattering Group
Electronic Liquid-Crystal Nature of Stripes
Doping Phase Diagram of LBCO at Ambient
Pressure Pressure Phase Diagram of LBCO at x1/8
CMPMS (Brookhaven)
DESY
M. v. Zimmermann

• J. M. Tranquada
• G. D. Gu
• C. C. Homes
• Z. J. Xu
• J. S. Wen

Washington University
M. Debessai J. S. Schilling
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Competing Order in Strongly Correlated Electron
Systems
heavy fermion superconductor
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Competing Order in Strongly Correlated Electron
Systems
La2-xBaxCuO4
1/8-problem
La2-xSrxCuO4
HTT
LTO
3D AF
LTT
stripes
Tc
SC
SG
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Common Conception LTT Phase Pins Stripes
LTO phase
Cu-O-Cu
LTT phase
Stripe Order
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Stripe Order in LBCO
magnetism
charge
Tranquada et al. Nature (1995)
Fujita et al. PRB (2004)
Stripes detected with neutrons, x-rays in LBCO,
LNSCO
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Electronic Liquid-Crystal
Kivelson et al. Nature (1998)
Hinkov et al., Science (2008) Ando et al., PRL
(2002)
Evidence in YBa2Cu3O6.45
Symmetry broken by orthorhombic structure
Stripe phase of La2-xBaxCuO4
At ambient pressure symmetry broken by LTT
structure
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Stripe Order in LBCO at Ambient Pressure
p 0 GPa
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Pressure Dependence of Tc
2 GPa
x1/8
Tc18K
Tc
0 GPa
0.125
SC
0.12 0.125 0.13
Ido et al. Physica C (1991)
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High Energy Single-Crystal X-ray Diffraction
under Pressure
sample
100 keV photons
BW5 _at_ DESY, Hamburg
Review of Scientific Instruments 79, 33906 (2008)
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Tuning the Structure with Pressure
p 0 GPa
SO
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Stripes in Tetragonal High Pressure Regime
(2, 0, 0)/(0, 2, 0) TTLT
TTLT
b
c
T10K
a
LTT
HTT
(22?, 0, 5.5)
pc
(1, 0, 0)
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Charge Stripes on Square Lattice

• High pressure 4-fold symmetric planes
• Charge stripes still develop
• Stripes spontaneously break Symmetry
• What pins stripes

PDF, XAFS

• PDF Tilted Octahedra even in the HTT Phase
• XAFS Local Tilts around Dopants

Billinge et al., PRL (1994)
Haskel et al., PRB (2000)
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Diffuse scattering in High Pressure Regime
(3/2 3/2 2)
20Å
40Å
80Å
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LBCO
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Nematic Patches in High Pressure Regime

• Commensurate patches of stripes and octahedral
  tilts
• Quenched disorder always a relevant pertubation
• Dopant disorder leads to finite size domains

nematic patches
E. Carlson et al., PRL (2006)
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Summary

• Stripes spontaneously break symmetry in HTT
  phase
• Pinned by quenched dopant disorder
• Supports electronic liquid-crystal picture of
  HTSC

Outlook

• c-axis correlations
• What happens for x?1/8 Ba
• What happens at higher pressures

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supplemental slides
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High Energy Single-Crystal X-ray Diffraction
under Pressure
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Different Models for the Stripe Phase
Electronic micro phase separation
J. Zaanen et al. PRB 40, 7391 (1989) V. Emery et
al., PRL 64, 475 (1990) S.R. White et al., PRL
80, 1272 (1998)
Fermi surface nesting SDW/CDW
Mason et al. PRL 77, 1604 (1996)
Spiral spin order
B. Shraiman, E.D. Siggia, PRL 62, 1564 (1989)
Hasselmann et al. PRB 69, 14424 (2004) Shushkov
et al. PRB 70, 245023 (2004)
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Question of Dimensionality (1D Stripes, 2D
Pattern)
Checkerboard electronic state in
Ca2-xNaxCuO2Cl2
T. Hanaguri et al., Nature 430, 1001 (2004)
Magnetic excitations in detwinned YBa2Cu3O6x
V. Hinkov et al., Nature 450, 650 (2004)
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Competing order in La2-xBaxCuO4
Ba doping
Maeno et al. PRB, 7753 (1991)
hole concentration of 1/8 crucial
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Competing order in La1.875Ba0.125CuO4
100 Ba
100 Sr
Tc31K
CO
Kimura et al., PRB 70, 134512 (2004)
Ba-doping is crucial
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Doping dependence
average structure
local distortions
electronic correlations
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Average Structure and Cation Size Variance
La1.85-yNdySr0.15CuO4
L1.85-yMyCuO4
Büchner et al. (1992) Wagener et al. PRB (1997)
McAllisten et al. PRB (2002)
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Detection of Charge and Spin Stripe Transition
La1.875Ba0.125CuO4
charge peak
LTO
TSO
LTT
Hc
spin
TSO
spin
Hab
TCO
WFM
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Stripe Order in LBCO at High Pressure?
I
?
charge
?
spin
T
SC
pressure
?
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Traveling-Solvent Floating-Zone Technique
feed rod
0.5mm/h
liquid zone
crystal
La2-xBaxCuO4 with x1/8
(G.D. Gu)
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Charge correlations along the c-axis
(0, 22?, L)
1D charge stripes
2D charge grid
c
c
c
k
h
M. Vojta et al., cond-mat/0408461
similar result La1.48Nd0.4Sr0.12CuO4 , x-rays,
T. Niemoeller et al., EPL (1998) La1.875Ba0.075Sr0
.05CuO4 , neutrons, H. Kimura et al., PRB (2003)
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Search for non-1D-Correlations
magnetism
charge
(0 2 ½)



(½ ½ 0)
Results for LBCO consistent with 1D-stripe model
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(1.5, 1.5, 2) T10K
(1, 0, 0) T10K
(22?, 0, 5.5) T10K
a
b
c
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Temperature dependence
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Detection of Charge and Spin Stripe Transition
La1.875Ba0.125CuO4
charge peak
LTO
TSO
LTT
Hc
spin
TSO
spin
Hab
TCO
WFM
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Pressure and Superconductivity
LSCO bulk
Hg-1223 bulk
LSCO thin film
buckled
flat
Bozovic et al. PRL (2002)
Gao et al. PRB (1994)
Yamada et al. JSSC (1989)
Pressure affects crystal structure and
electronic band structure
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ARPES
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Stripes vs. CDW
T. Valla et al., Science (2007)
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ARPES
T. Valla et al., Science (2007)