Charge%20Inhomogeneity%20and%20Electronic%20Phase%20Separation%20in%20Layered%20Cuprate

1
Charge Inhomogeneity and Electronic Phase
Separation in Layered Cuprate
F. C. Chou Center for Condensed Matter Sciences,
National Taiwan University National Synchrotron
Radiation Research Center, Taiwan
2
Inhomogeneous Electron Density
3
CDW, Dimerization and Nesting
1d Peierls instability q 2kF CDW gt MIT 2d
Fermi Surface nesting
Peierls Transition
4
Phase Diagrams
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Charge Inhomogeneity Spin and charge stripes
La2-x-yNdySrxCuO4

• Holes segregate into AF antiphase domain walls

Tranquada et al, Nature 1995
6
Spin/Charge Stripes and Superconductivity
Yamada et al, PRB 1998
7
1d domain walls in low x La2-xSrxCuO4
Cho et al, 1993
8
Charge Inhomogeneity Checkerboard Type
Underdoped Bi2Sr2CaCu2O8d
Underdoped Ca2-xNaxCuO2Cl2
Hanaguri et al, Nature 2004
Hashimoto et al, PRB 2006
9
Electrochemical oxygen intercalation
Grenier et al, Physica C 1991
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Macroscopic Phase Separation in La2CuO4d
La2CuO4d

• Electrochemical oxygen intercalation
• Undoped AF domain and hope-doped SC domain

Radaelli et al, PRB 1993 Statt et al, PRB 1995
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Spinodal Decomposition
12
Staging charge/oxygen segregation
Wells et al, Science 1997
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Electrochemical oxygen intercalation
Grenier et al, Physica C 1991
14
La2-xSrxCuO4d hole doping through Srx and Od

• Identical SC onset 40K
• SC volume fraction indep. of x or d

15
La2-xSrxCuO4d magnetic phase by ZF-mSR

• Magnetic static ordering onset near 40K
• Magnetic volume fraction independent of x or d

16
Phase Separation?

• Co-existing superconducting (SC) and magnetic
  (ISDW) phases
• Identical SC and ISDW onsets
• SC phase grows at the expense of ISDW phase
• Chemical or Electronic origin?

17
Revisit LTT and ISDW
La2-xBa1/8CuO4 Non-SC La2-xSrxCuO4d SC
Structure ordering LTT LTO
Magnetic ordering 38K 3.5MHz 40K 3.5MHz

• Competing SC and ISDW, not LTT and ISDW

Luke et al, Physica C 1991
18
LTT and 1/8 dip of Tc
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Why Electronic Phase Separation?

• t-J model by Emery and Kivelson
• Holes tend to phase separate but long-range
  Coulomb repulsion frustrates phase separation
• Competing AF correlation and Coulomb interaction

• quantum confinement, paired electrons
• Wigner crystal?

Löw, Emery, Fabricius, and Kivelson, PRL 1994
Xiuqing Huang, cond-mat/0606177
20
Summary and Conclusions

• Large unexplored phase space
• PS of electronic origin indep. of x or d alone,
  identical ISDW phase, competing SC and static
  magnetic phases
• Competing SC and ISDW, not SC and LTT
• The electronic interaction of the doped holes is
  the primary driver of the phase separation rather
  than specific chemistry of O or Sr in this
  compound

Collaborators Hashini Mohottala and Barry Wells
(U. Conn.) et al, Nature Materials 2006
21
Wigner crystals
Phys. Rev. Lett. vol. 86, p. 3851 (2001)
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Stripes in La2-xSrxCuO4
Marouchkine, 2006
Fujita et al, RRB 2002
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Staging behavior neutron scattering
PHYSICAL REVIEW B 69, 020502 (2004)