Electron-Electron Correlation Effects in Low-Dimensional Conductors and Superconductors

Advances in the physics and chemistry of low-dimensional systems have been really magnificent in the last few decades. Hundreds of quasi-one-dimensional and quasi-two-dimensional systems have been synthesized and studied. The most popular representatives of quasi-one-dimensional materials are polyacethylenes CH [1] and conducting donor-acceptor molecular crystals TIF­ z TCNQ. Examples of quasi-two-dimensional systems are high temperature su­ perconductors (HTSC) based on copper oxides LA2CU04, YBa2Cu306+y and organic superconductors based on BEDT -TIP molecules. The properties of such one- and two-dimensional materials are not yet fully understood. On the one hand, the equations of motion of one-dimensional sys­ tems are rather simple, which facilitates rigorous solutions of model problems. On the other hand, manifestations of various interactions in one-dimensional systems are rather peculiar. This refers, in particular, to electron--electron and electron-phonon interactions. Even within the limit of a weak coupling con­ stant electron--electron correlations produce an energy gap in the spectrum of one-dimensional metals implying a Mott transition from metal to semiconductor state. In all these cases perturbation theory is inapplicable. Which is one of the main difficulties on the way towards a comprehensive theory of quasi-one-dimensional systems. - This meeting held at the Institute for Theoretical Physics in Kiev May 15-18 1990 was devoted to related problems. The papers selected for this volume are grouped into three sections.

Contenu

I Correlation Effects in Low-Dimensional Conductors, Superconductors and Model Systems.- The 1-d Hubbard Model: A Landau Luttinger Liquid.- Mean-Field Study of Possible Electronic Pairings in the CuO Plane of HTSO.- Correlation Pairing and Antiferromagnetic Phase Energy in Low-Dimensional Systems of La-Sr-Cu-O and Y-Ba-Cu-O Metaloxides.- Kink Nature of Current Carriers in High-Tc Superconductor Oxides.- Anomaly Index and Induced Charge on a Noncompact Surface in an External Magnetic Field.- About the Influence of Uniaxial Pressure on the Twin Structure in the 1-2-3 System.- II Correlation Effects in Organic Crystals, Molecules and Polymers.- Coexistence of Mott and Peierls Instabilities in Quasi-One-Dimensional Organic Conductors.- Nonlinear Optical Susceptibility for Third Harmonic Generation in Combined Peierls Dielectrics.- Nonlinear Optical Properties of (A - B)x-Polymers.- Application of the Method of Cyclic Permutations to the Calculation of Many-Electron Systems. Polaron States in the Emery Model.- From Incomplete Allowance for Electron Correlation to the Full CI in ?- Systems. The Variational Operator Approach.- Dynamical Correlation in Finite Polymethine Chains.- Electronic Structure and Optical Spectra of Transition Metal Complexes via the Effective Hamiltonian Method.- III Multiparticle Effects in Kinetics and Magnetism.- Magnetic Properties of the Hubbard Model with Infinite Interactions.- Anomalous Transport Through Thin Disordered Layers.- Correlation Effects in Many-Body Reactive Systems.- Fermionization of a Generalized Two-Dimensional Ising Model.- Ferromagnetism of Charge-Transfer Crystals: Curie Temperature of a Organometallic Ferromagnet.- Index of Contributors.