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Electronic band structure and photoemission: A review and projection

Description: A brief review of electronic-structure calculations in solids, as a means of interpreting photoemission spectra, is presented. The calculations are, in general, of three types: ordinary one-electron-like band structures, which apply to bulk solids and are the basis of all other calculations; surface modified calculations, which take into account, self-consistently if at all possible, the presence of a vacuum-solid interface and of the electronic modifications caused thereby; and many-body calculations, which go beyond average-field approximations and consider dynamic rearrangement effects caused by electron-electron correlations during the photoemission process. 44 refs.
Date: September 1, 1987
Creator: Falicov, L.M.
Partner: UNT Libraries Government Documents Department

Superconductivity: Phenomenology

Description: This document discusses first the following topics: (a) The superconducting transition temperature; (b) Zero resistivity; (c) The Meissner effect; (d) The isotope effect; (e) Microwave and optical properties; and (f) The superconducting energy gap. Part II of this document investigates the Ginzburg-Landau equations by discussing: (a) The coherence length; (b) The penetration depth; (c) Flux quantization; (d) Magnetic-field dependence of the energy gap; (e) Quantum interference phenomena; and (f) The Josephson effect.
Date: August 1, 1988
Creator: Falicov, L.M.
Partner: UNT Libraries Government Documents Department

Spin waves at surfaces and steps in ferromagnets and antiferromagnets

Description: The study of the properties of elementary magnetic excitations - spin waves or magnons - in the neighborhood of surfaces, discontinuities, defects, and impurities is an active field of solid-state magnetism. These modes are of interest for understanding relaxation phenomena as well as chemical reactions catalyzed by magnetic substrates. In this contribution we would like to report two different results: (1) some spectra of the spin-wave modes associated with clean and stepped surfaces of a ferromagnet - the clean and a stepped (001) surface of a face-centered-cubic solid; and (2) the unusual and yet unresolved difficulties encountered when similar procedures are attempted on antiferromagnetic surfaces and steps.
Date: August 1, 1981
Creator: Falicov, L.M.
Partner: UNT Libraries Government Documents Department

Open problems in condensed matter physics, 1987

Description: The 1970's and 1980's can be considered the third stage in the explosive development of condensed matter physics. After the very intensive research of the 1930's and 1940's, which followed the formulation of quantum mechanics, and the path-breaking activity of the 1950's and 1960's, the problems being faced now are much more complex and not always susceptible to simple modelling. The (subjectively) open problems discussed here are: high temperature superconductivity, its properties and the possible new mechanisms which lead to it; the integral and fractional quantum Hall effects; new forms of order in condensed-matter systems; the physics of disorder, especially the problem of spin glasses; the physics of complex anisotropic systems; the theoretical prediction of stable and metastable states of matter; the physics of highly correlated states (heavy fermions); the physics of artificially made structures, in particular heterostructures and highly metastable states of matter; the determination of the microscopic structure of surfaces; and chaos and highly nonlinear phnomena. 82 refs.
Date: August 1, 1988
Creator: Falicov, L.M.
Partner: UNT Libraries Government Documents Department

High-resolution EPR and piezospectroscopy studies of the lithium-oxygen donor in germanium

Description: Lithium-oxygen donors in germanium were studied at low concentration (< 10/sup 14/ cm/sup -3/) by means of Electron Paramagnetic Resonance and Photoelectric Piezospectroscopy. We find unambiguously four equivalent real-space positions with <111> symmetry, which together with the four-valley conduction band lead to a 16-fold ground state. The system exhibits dynamic tunneling between the four equivalent orientations.
Date: September 1, 1978
Creator: Haller, E.E. & Falicov, L.M.
Partner: UNT Libraries Government Documents Department

Electronic and magnetic structure of chromium surfaces and chromium monolayers on iron

Description: Chromium surfaces and Cr monolayers atop Fe have greatly enhanced magnetizations relative to bulk. The Cr (100) surface is ferromagnetic with a spin polarization of 3.00; the (110) surface is antiferromagnetic. A Cr monolayer is ferromagnetic atop either the (100) or (110) Fe surfaces; the former has a large polarization of 3.63.
Date: May 1, 1985
Creator: Victora, R.H. & Falicov, L.M.
Partner: UNT Libraries Government Documents Department

Electronic and magnetic properties of transition-metal surfaces, interfaces and overlayers

Description: Results of calculations for the electronic and magnetic properties of transition-metal surfaces, interfaces and overlayers are presented for a variety of systems. They involve Ni, Co, Fe and Cr in a diversity of forms, including alloys, metastable configurations, and overlayers on nonmagnetic metals. The overall behavior of these systems can be interpreted in terms of four qualitative rules which are presented, analyzed, and illustrated.
Date: August 1, 1984
Creator: Falicov, L.M.; Victora, R.H. & Tersoff, J.
Partner: UNT Libraries Government Documents Department

A DONOR COMPLEX WITH TUNNELING HYDROGEN IN PURE GERMANIUM

Description: A shallow donor complex observed by several authors in ultrapure germanium grown in a hydrogen atmosphere is attributed to an oxygen-hydrogen system. Photoconductivity data under stress are presented. An abrupt transition in the spectra at a well-defined stress (2.1 x 10{sup 8} dyn cm{sup -2}) is found. It is explained by a theory which involves dynamic tunneling of the hydrogen in the vicinity of an oxygen center. The comparison with other complex donors and acceptors supports the model.
Date: February 1, 1980
Creator: Joos, B.; Haller, E.E. & Falicov, L.M.
Partner: UNT Libraries Government Documents Department

Cluster-Variation Method for the Triangular Lattice Gas [Part] 1. Three-Sublattice Point Approximation

Description: The triangular lattice gas is examined as a model for the ordering of Li{sup +} ions in intercalated transition metal dichalcogenides. A three-sublattice Bragg~ Williams (point approximation) calculation illustrates the meaning of the features in the incremental capacity versus concentration curves: (a) minima are associated with ordered structures, (b) sharp maxima (divergences) are caused by the coexistence of ordered and disordered phases over small concentration intervals and (c) smooth maxima can be found at concentrations of no direct relevance to ordering.
Date: August 1, 1980
Creator: Osorio, R. & Falicov, L. M.
Partner: UNT Libraries Government Documents Department

Cluster-Variation Method for the Triangular Lattice Gas [Part] 2. Triangle Approximation

Description: A triangular lattice gas with nearest~neighbor repulsions and three-particle attractions is examined in a three-sublattice triangle approximation as a model for lithium intercalation in the transition metals dichalcogenides. Order-disorder phase diagrams and thermodynamic functions are computed. Peaks in the incremental capacity as function of concentration in the experimental data of Thompson are reproduced in our model.
Date: August 1, 1980
Creator: Osorio, R. & Falicov, L. M.
Partner: UNT Libraries Government Documents Department

Three-Sublattice Model for a Triangular Lattice Gas

Description: A three-sublattice Bragg-Williams model of a triangular lattice gas with repulsive nearest-neighbor interactions is presented. It is intended to represent intercalated Li{sup +} in Li{sub x}TiS{sub 2} . An order-disorder phase diagram and thermodynamic functions are computed. In particular the incremental capacity is calculated and compared with the experimental data of Thompson. It is found that (a) ordering results ln minima in the incremental capacity, (b) sharp maxirna (divergences) are caused by small regions of two-phase coexistence and (c) smooth maxima are found at concentrations of no relevance to ordering.
Date: March 1, 1980
Creator: Osorlo, R. & Falicov, L. M.
Partner: UNT Libraries Government Documents Department

Magnetic, optical and charge-transfer spectra of antiferromagnetic solid {alpha}-O{sub 2} and ``paramagnetic`` solid {beta}-O{sub 2}: A small-cluster, many-electron calculation

Description: The electronic spectra of {alpha} and {beta} solid O{sub 2} were calculated in a full many-body approach for a cluster consisting of four O{sub 2} molecules with periodic boundary conditions. By including only the partially occupied {pi} orbitals (16 spin-orbitals, 8 electrons) the basis set consists of 12870 many-electron states. Use of the symmetry properties (group-theoretical analysis) simplifies the problem considerably. Resulting spectra -- with phenomenological Hamiltonian parameters obtained from experiment -- consist of separate regions: (a) 81 states corresponding to the ground state and low-energy magnetic excitations (magnons); (b) 1215 states of neutral molecular excitations (excitons); and (c) 11574 charge-transfer states (conducting high-energy states). Analysis of the properties of the ground states in both {alpha} and {beta} solid O{sub 2} has been carried out.
Date: October 1, 1993
Creator: da Silva, A. J. R. & Falicov, L. M.
Partner: UNT Libraries Government Documents Department

Surface, interface and thin-film magnetism

Description: In the last quarter of the 20th century, with the information revolution and the ever growing need to acquire, store, and retrieve information, the science and technologies attached to magnetic recording have experienced an explosive growth. Central to those pursuits has been the materials science of magnetism as it applies to surfaces, interfaces, and thin films. This report discusses topics on thin-film magnetism such as: theory, physical effects, prospects, opportunities and future developments. (JL)
Date: July 1, 1991
Creator: Falicov, L.M. (Lawrence Berkeley Lab., CA (United States) California Univ., Berkeley, CA (United States). Dept. of Physics)
Partner: UNT Libraries Government Documents Department