High Tc Superconductivity And Magnetism In T J And T T J Models

In the last few years, the use of numerical methods as Monte Carlo, stochastic models and strongly correlated systems close to phase transitions, has increased exponentially with unexpected success also in fields really faraway from physics as for example biology, chemistry, finance, sociology and climatology. In this book we expose a new Monte Carlo variational approach applied to t-J and t-t -J Models for describing the experimental phase diagram of the High-Tc Superconductors that after more than 20 years is still an open and amazing problem. We focused our analysis on phase separation, d-wave superconductivity and magnetic properties and thanks to our method we were able to describe the main experimental results on the phase diagrams of the High-Tc materials, highlighting the key factors involved which are at the basis of their strange behaviour. This work should be especially useful to all scientists interested in strongly correlated systems and numerical methods as starting point for further studies on High-Tc superconductors or for PhD courses with the target of introduce to numerical methods and their applications to correlated systems.

The articles in this exceptional book contain regular papers, extended papers and reviews, and thus vary in length and are useful for all kinds of audience. They describe, as the book's name suggests, HTSC models and methodologies. Physical models (like extended BCS model, bipolaron model, spin bag model, RVB (resonating valence bond) model, preformed Cooper pairs and antiferromagnetic spin fluctuation (AFSF) based models, stripe phase, paired cluster (spin glass (SG) frustration based) model, Kamimura-Suwa (Hund's coupling mechanism based) model, electron- plasmon interaction, electron- phonon interaction, etc.), theoretical methods (methodologies) (like generalised BCS-Migdal-Eliashberg theory, Hubbard model, t-J model, t-t'-U model, Hubbard-Holstein model, Fermi-, non Fermi- and marginal Fermi- liquid concepts, generalised Hartree-Fock formalism, etc.) and, experimental status and methodologies are all described there. For comparison with cuprates, fullerenes, ruthenates, organic-, non Cu-containing oxide-and conventional (elemental, A15)- superconductors, molecular crystals, nickelates, manganites, borides etc. are also discussed.

"High-Tc Superconductivity" is based on a meeting held in Kiev and contains contributions discussing the most recent achievements in this field. The book includes reviews and original papers covering theoretical and experimental aspects of the subject. Keywords: electronic and magnetic properties, metallization processes, emission and optic spectra, lavitation, pinning, frustration and fluctuations, thin films

This book is a collection of the chapters intended to study only practical applications of HTS materials. You will find here a great number of research on actual applications of HTS as well as possible future applications of HTS. Depending on the strength of the applied magnetic field, applications of HTS may be divided in two groups: large scale applications (large magnetic fields) and small scale applications (small magnetic fields). 12 chapters in the book are fascinating studies about large scale applications as well as small scale applications of HTS. Some chapters are presenting interesting research on the synthesis of special materials that may be useful in practical applications of HTS. There are also research about properties of high-Tc superconductors and experimental research about HTS materials with potential applications. The future of practical applications of HTS materials is very exciting. I hope that this book will be useful in the research of new radical solutions for practical applications of HTS materials and that it will encourage further experimental research of HTS materials with potential technological applications.

A theoretical model for the explanation of low - temperature properties of modern high-Tc superconducting compounds is proposed. The microscopic theory of superconductivity is developed based on anisotropic properties of newly discovered compounds. The book treats such important issues in HTSC like: the influence of impurity on SC, SC in disordered non-adiabatic systems, the coexistence of spin density wave and SC, the microscopic theory of thermodynamic properties of anisotropic two-band systems such MgB2. Thus, the book is the base for understanding the phenomena and the processes which take place in modern anisotropic HTSC. The mathematical methods which permit to obtain concrete results on thermodynamic, magnetic and kinetic properties of SC give a special value to this book. The book is addressed to theoretical physicists and experimenters, Ph. D. and postdoctoral students working in SC. The book may be used as a base for a course within master's degree program in solid state matter. Recommended by the Scientific Council of Institute of Applied Physics of Moldavian Academy of Science.

A broad introduction to high Tc superconductors, their parent compounds and related novel materials, covering both fundamental questions of modern solid state physics (such as correlation effects, fluctuations, unconventional symmetry of superconducting order parameter) and applied problems related to short coherence length, grain boundaries and thin films. The information that can be derived from electron spectroscopy and optical measurements is illustrated and explained in detail. Descriptions widely employ the clear, relatively simple, phenomenological Ginzburg-Landau model of complex phenomena, such as vortex physics, vortex charge determination, plasmons in superconductors, Cooper pair mass, and wetting of surfaces. The first comprehensive reviews of several novel classes of materials are presented, including borocarbides and chain cuprates.

High-temperature (high-Tc) superconductivity is a fascinating field in condensed matter physics research. After more than twenty-five years of research, the origin of high-Tc superconductivity is still not clear. To understand the microscopic pairing mechanism and to explain high-Tc superconductivity are for academic and technical reasons of great interest. This book is focused on the studies of superconducting (SC) and magnetic properties in two classes of high-Tc superconductors. Namely, in the novel Fe-based compounds Eu122, BaRb122 and in the cuprate system LBCO with 1/8 doping. The combination of muon-spin rotation, nuclear magnetic resonance, magnetization, and x-ray experiments allowed to probe the properties at the microscopic and macroscopic level. As a result, the superconducting and magnetic phase diagrams with respect to charge carrier doping as well as chemical and hydrostatic pressure were obtained. The phase diagrams cover the transition temperatures, the ordered moments and the volume fractions. The obtained phase diagrams revealed that, in the systems studied, superconductivity and magnetism are competing orders.

In this talk the author introduces a method of diagonalization in a systematically expanded Hilbert space. The author shows some applications of this procedure to several models of relevance to high-Tc superconductivity like the t-J, the t-J{sub z} and Hubbard models. Finally, the author discusses the relation of this method of diagonalization in a reduced Hilbert space with perturbation theory and with variational methods.