The understanding of electronic behaviour in solids when (some of) the valence electrons have both localized and band-like characteristics is one of the central problems of physics and chemistry in the second half of this century. Many advances have indeed been made using highly sophisticated techniques and concepts. Our objectives in bringing together specialists from different areas was cross-fertilization of ideas and redefinition of bottlenecks and problems. The testimony of the participants and the book which follows indicate a fair degree of success. This book is a record of discussions aimed at digestion and reassessment of some of the recent major advances in our understanding of narrow bands. Note that we expressly asked participants to give a short readable account of the major problems in their field and not to emphasize their latest results to be as "technical" as they might be in a normal scientific article. We did not ask for complete reviews of what was going on in the field and this book should not be read as such. Neither should it be approached as the sort of educational text which the NATO ASI proceedings are supposed to be. We have tried to produce a useable account of a workshop in which an attempt was made to define real problems and to distinguish them from illusory problems.
Table of ContentsTo The Book.- A. Ground State and Near Ground State Phenomena.- 1. From transition metals to normal rare earth metals via heavy fermion systems.- 2. Quasiparticles in narrow band systems.- 3. Dynamical magnetic fluctuations in narrow band metals.- 4. The role of Fermi surface anisotropies in Heavy-fermion Superconductors.- 5. Ordering phenomena in heavy-fermion compounds.- 6. Gaining control over rare earth valence fluctuations.- 7. Narrow linewidth phenomena of dilute d and f atoms in metals.- 8. Point-contact spectroscopy in a heavy-fermion metal: UPt3 vs Cu.- 9. “Soft”-versus “hard” spectroscopies for narrow band materials.- B. Theoretical Descriptions of the Ground State.- 10. Bandstructure and localized descriptions of narrow band systems.- 11. The Molecular Orbital cluster model approach to electronic structure.- 12. Variational Monte-Carlo method for strongly interacting electrons.- 13. Theory of Mott insulators.- 14. Qualitative considerations on transition metal compounds.- 15. The character of band gaps in transition metal compounds.- 16. Narrow band and localization.- 17. Model Hamiltonians and how to determine their parameters.- 18. Local density calculated parameters for the Anderson Hamiltonian.- Some points from the discussion.- C. High Energy Spectroscopies of Narrow Band Materials.- 19. High energy spectroscopies.- 20. High energy spectroscopies as a probe of hybridization, Coulomb correlation energies and occupancies in narrow band systems: Discussion paper.- 21. Observation of low-energy excitations in lanthanide materials by high-resolution photoemission.- 22. The importance of atomic relaxation in core-level spectra for narrow-band systems.- 23. Final state interaction in L3 absorption spectra of Ce and La compounds.- 24. The influence of electronic polarization on the core XPS spectra of Ce-compounds.- Some points from the discussion.- D. High Temperature Superconductors.- 25. Superconducting oxides.- 26. What chemistry is there in high temperature superconductivity? Low energy scale properties of narrow band systems.- 27. Some recent experiences in narrow band phenomena: URu2Si2 and YBa2Cu3O7.- 28. Valence fluctuations in La2-xSrxCuO4.- Compound Index.