Charge Inhomogeneity and Electronic Phase Separation in Layered Cuprate

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 => MIT 2d Fermi Surface nesting Peierls Transition

4. Phase Diagrams La2CuO4+d La2-xSrxCuO4

5. 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 L ~ 1/x Finite size effect: 1-TN(x)/TN(0) ~ L-1/n Cho et al, 1993

8. Charge Inhomogeneity: Checkerboard Type Underdoped Bi2Sr2CaCu2O8+d Underdoped Ca2-xNaxCuO2Cl2 Hanaguri et al, Nature 2004 Hashimoto et al, PRB 2006

9. Electrochemical oxygen intercalation La2CuO4+d V Reference Pt La2CuO4 NaOH/H2O electrolyte Li et al, PRL 1996 Grenier et al, Physica C 1991

10. Macroscopic Phase Separation in La2CuO4+d La2-xSrxCuO4 La2CuO4+d • Electrochemical oxygen intercalation • Undoped AF domain and hope-doped SC domain Radaelli et al, PRB 1993; Statt et al, PRB 1995

11. Spinodal Decomposition

12. Staging: charge/oxygen segregation La2CuO4+d Wells et al, Science 1997

13. Electrochemical oxygen intercalation La2CuO4+d La2-xSrxCuO4 V Reference Pt La2CuO4 NaOH/H2O electrolyte Grenier et al, Physica C 1991

14. La2-xSrxCuO4+d: hole doping through Srx and Od • Identical SC onset ~40K • SC volume fraction indep. of x or d

15. La2-xSrxCuO4+d: magnetic phase by ZF-mSR La1.91Sr0.09CuO4+d • 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 • Chemicalor Electronic origin?

17. Revisit LTT and ISDW • Competing SC and ISDW, not LTT and ISDW Luke et al, Physica C 1991

18. LTT and 1/8 dip of Tc

19. Why Electronic Phase Separation? t-J model by Emery and Kivelson: “Holes tend to phase separate but long-rangeCoulomb 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)

22. Stripes in La2-xSrxCuO4 Marouchkine, 2006 Fujita et al, RRB 2002

23. Staging behavior – neutron scattering PHYSICAL REVIEW B 69, 020502 (2004)