Phase Separation in Cuprate Superconductors : Proceedings of the second international workshop on ¿Phase Separation in Cuprate Superconductors¿ September 4 ¿ 10, 1993, Cottbus, Germany

Written by leading experts including Nobel prize winner K.A. Müller the articles in this book review recent advances in our understanding of the nature of high-Tc cuprate superconductors, covering both material properties and the mechanism of superconductivity.

I General Properties.- Recipe for High-Tc Transition-Metal Chalcogenide Superconductors.- 1. Introduction.- 2. The Properties.- 3. Conclusions.- Phase Separation as a Possible Scenario for High Tc Superconductors: A Particular Overview.- 1. Introduction.- 2. Phase separation: a relevant issue.- 3. A specific example.- Point Contact Spectroscopy in the High Tc Oxides.- 1. Introduction.- 2. Energy gap and Fermi velocity determination. The Eliashberg interpretation.- 3. The electron phonon interaction in La1.85Sr0.15CuO4.- 4. Conjectures on the strong electron phonon and correlations interactions scenario - and some consequences regarding phase separation.- Cuprate Superconductors: Universal Properties and Trends; Evidence for Bose-Einstein Condensation.- 1. Universal Properties and Trends.- 2. Evidence for Bose-Einstein Condensation.- 3. Conclusion.- II Electronic Results I.- Polar on Formation and Percolative Phase Separation in HTSC.- 1. Introduction.- 2. Hole dynamics in CuO2 planes.- 2.1 Doped system.- 3. Two-particle states.- 4. Conditional hopping in one- and three band Hubbard models.- 4.1 One-band model for spin-conditioned hopping.- 5. Concluding remarks.- On the Role of Electronic and Chemical Phase Separation: Susceptibility and Conductivity Experiments on La2?xCuO4+?.- 1. Introduction.- 2. Electronic Phase Separation.- 2.1 Quasiparticles.- 2.2 Phase Separation and Metalization.- 2.3 Counterions; chemical versus electronic phase separation.- 3. Experimental.- 4. Results and Discussion.- 4.1 Conductivity experiments.- 4.2 Equilibration and annealing experiments.- 5. Summary and Conclusions.- The Phase Diagrams and Doped-Hole Segregation in La2CuO4+? and La2?xSrxCuO4+? (x ? 0.15, ? ? 0.12).- 1. Introduction.- 2. The La2CuO4+? System.- 2.1 Relationship Between Tps and TN.- 2.2 La2CuO4+? Phase Diagram and Structures.- 2.3 The Oxidation State(s) of the Excess Oxygen and the Doped- Hole Concentration in the CuO2 Plane.- 2.4 Single Crystal Synthesis and Characterization.- 2.5 Dependence of Superconducting Properties on Temperature and Pressure History.- 3. The La2?xCuO4+? System.- 3.1 The La2?xSrxCuO4 System (? = 0).- 4. Concluding Remarks.- Neutron Spectroscopy in RBa2Cu3Ox (R=Rare Barth, 6?x?7) Compounds: Charge Transfer, Phase Separation, Spin Fluctuations.- 1. Introduction.- 2. CEF excitations in ErBa2Cu3Ox (6 ? x ? 7).- 3. Analysis of the CEF results obtained for ErBa2Cu3Ox.- 3.1 Charge transfer.- 3.2 Phase separation.- 3.3 Percolative superconductivity.- 4. Fractal sizes of the clusters.- 5. Low-energy Cu2+ spin fluctuations.- 5.1 Introductory remarks.- 5.2 Asymmetric line shape of CEF transitions in Ho0.1Y0.9Ba2Cu3O7.- 5.3 Neutron scattering from spin-polarized clusters.- 6. Conclusion.- III Electronic Results II.- Phase Separation in Cuprate Superconductors: Magnetic Resonance Studies.- 1. Introduction.- 2. Experimental details.- 3. Results and discussion.- 4. Summary.- Paramagnetic Resonance Studies of Phase Separation in Cuprate Superconductors.- 1. Introduction.- 2. Investigated materials and experimental details.- 3. Experimental results.- 3.1 La2CuO4+? ceramics.- 3.2 La2CuO4+? single crystal.- 3.3 La2?xSrxCuO4+? ceramics.- 4. Discussion.- Fermi Glass State in Partially Doped Insulating Cuprates.- 1. Introduction.- 2. Dark transport in partially doped insulating cuprates.- 3. Conductivity under photoexcitation.- 4. Spectral response of the photoconductivity in partially doped insulating cuprates.- 5. Supporting evidence of the Fermi-glass state from ARPES, NQR and other experiments.- 6. Discussions and Remarks.- Two-Magnon Raman Scattering in Doped YBa2Cu3Ox with Respect to Confined Hole Clusters.- 1. Introduction.- 2. Light scattering of spin fluctuations.- 3. Results.- IV NMR and Mössbauer Studies.- Electron Hole Ordering in La2CuO4+?.- 1. Introduction.- 2. Spin dynamics in as-prepared and Sr-doped La2?xSrxCuO4.- 3. Spin dynamics in electrochemically oxidized La2CuO4+?.- 4. Comparison of 1/T1*, LFS and dc susceptibility measurements.- 5. The percolation model.- 6. A Ginsburg-Landau-Wilson model for phase separation.- 7. Summary.- Microscopic Study of Local Structure and Charge Distribution in Metallic La2CuO4+?.- 1. Introduction.- 2. Macroscopic phase separation.- 3. Cooling rate dependence of Tc.- 4. Determination of local structure and local charge environments.- 4.1 La NQR.- 4.2 La NMR.- 4.3 Cu NQR.- 5. Interpretation and discussion.- 6. Conclusions.- Mössbauer Probe Measurements in La2?xSrxCuO4 and YBa2Cu3Ox.- 1. Mössbauer emission measurements on highly dilute 57Fe impurities in La2?xSrxCuO4.- 1.1 57Co doping process.- 1.2 57Fe room temperature emission measurements.- 1.3 57Fe low temperature emission measurements.- 1.4 Discussion and conclusions.- 2. Local properties of substituted YBa2Cu3Ox examined by Mössbauer Spectroscopy on Yb3+ ion probes.- 2.1 Influence of the spatial distribution of oxygen on the magnetic properties of YBa2Cu3O6.55.- 2.2 Influence of cationic substitutions.- 2.3 Zn2+ substitution.- 2.4 Pr3+ substitution.- 2.5 Summary and Discussion.- V Structural Phase Separation.- Indications for a Phase Separation in YBa2Cu3O7?x.- 1. Introduction.- 2. Synthesis of the samples.- 3. X-ray lattice constants.- 4. Neutron diffraction.- 4.1 Experimental.- 4.2 Anomalies in the Cu-O bond lengths.- 5. Magnetization measurements.- 6. Oxygen diffusion and Tc splitting.- 7. Conclusions.- Superconductivity Versus Oxygen Concentration in 123 Compounds: Influence of RE Ionic Radii Studied by Cu NQR.- 1. Introduction.- 2. Tc versus x for different RE in REBa2Cu3Ox.- 3. Cu NQR lines in different configurations.- 4. Experimental details.- 5. Results.- 5.1 NQR of Tm123.- 5.2 NQR of Nd123.- 6. Discussion.- 7. Conclusion.- The Role of the Additional Oxygen Atoms on the Superconducting Properties of La2CuO4-Related Compounds.- 1. Introduction.- 2. Experimental and Results.- 2.1 Potentiostatic experiments on ceramics.- 2.2 Galvanostatic experiments on ceramics.- 2.3 Electrochemical oxidation of thin films.- 2.4 Electrochemical oxidation of crystals.- 2.5 Role of the additional oxygen atoms.- 2.6 Mobility of “O?” in oxide lattices.- 3. Conclusion.- Structural Disorder and Phase Separation in TmBaCuO as Seen from Tm NMR.- 1. Experimental.- 2. Mean length of CuO chain segments.- 3. Localized Cu2+ centers.- 4. Phase separation in underdoped TmBa2Cu3O6+x.- VI Electron-Phonon Interaction I.- The Coupling of a Wigner Polaronic Charge Density Wave with a Fermi Liquid Arising from the Instability of a Wigner Polaron Crystal: A Possible Pairing Mechanism in High Tc Superconductors.- 1. Introduction.- 2. The Polaron Size and its Temperature Dependence.- 3. The Polaron Pair Filling Factor and the Insulator to Metal Transition.- 4. Ordering of Polarons as Function of Doping.- 5. Partial Charge Density for the Polaron Gas and the Fermi Liquid.- 6. The Polaron Gas Condenses in a Generalized Wigner CDW at v = 1 and in a Generalized Wigner Crystal at v = 2.- 7. On the Pairing Mechanism.- Pairing Interaction and Phonon Renormalization Favored by Phase Separation.- 1. Introduction.- 2. Unitary transformations.- 3. The Cooper pair interaction.- 4. The phonon renormalization.- 5. Appendix.- Electronic Excitations in Undoped and Lightly Oxygen Doped La2CuO4+y.- 1. Introduction.- 2. Charge-Transfer Excitation.- 3. Crystal-Field Excitations.- 4. Impurity Absorption.- 5. Conclusion.- VII Electron-Phonon Interaction II.- Electronic Structure and High Tc Superconductivity in the Cuprates.- 1. Introduction.- 2. Band structure of the cuprates.- 3. The Labbé Bok formula.- 4. The Coulomb repulsion between electrons.- 5. Coherence length and anisotropy effects.- 6. Phase separation and conclusion.- Apex Oxygen Anharmonicity and Low Energy Electronic Transitions Observed in 1-2-3 by IR-Excited Raman Spectroscopy.- 1. Introduction.- 2. IR excited FT-Raman spectroscopy.- 3. YBa2Cu3O6+x (x ? 2): IR-Raman scattering at low oxygen concentration.- 4. ErBa2Cu3O6+x: 0.1 ? x ? 0.9.- 5. 18O Metallic YBa2Cu3O6+x Substituted Samples.- 6. Untwinned 1-2-3 Crystal: Electronic Background.- Photoexcited Electons and Holes in YBa2Cu3O7??: A Study by Picosecond Raman Scattering.- 1. Introduction.- 2. Photoinduced carriers.- 3. Photoinduced (super)conductivity and the effects of carriers on Raman spectra.- 4. Discussion.- 5. Conclusion.- Anharmonic Effects Related to the Apical Oxygen Vibration in YBa2Cu3O7 by LAPW Calculations.- 1. Introduction.- 2. Method.- 3. Results.- VIII Further Theoretical Concepts.- Thermodynamics of the Emery Model.- 1. Introduction.- 2. Phase Diagrams Including Separated Phases.- 3. A Strong Coupling Ansatz for the Emery Model.- 4. Spiral Magnetic Order.- 5. Self Energy and DOS in Weak Coupling.- 6. Conclusions.- The Effect of Coulomb Interactions on Phase Separation.- 1. Introduction.- 2. The Phase Diagram.- 3. The Structure of the Ground States.- 4. Conclusion.- Options for the Effective Electron-Electron-Interaction from Unitary Transformations.- 1. Introduction.- 2. Unitary Transformations in Physics.- 3. Fröhlich’s Transformation.- 4. Moving Base Transformations.- 4.1 Moving Base in Q.- 4.2 Moving Base in P.- 5. A Didactical Cu - O - Cu Model.