Coherent potential approximation

About: Coherent potential approximation is a research topic. Over the lifetime, 1930 publications have been published within this topic receiving 36805 citations.

Magnetic Anisotropies in Nanostructured Matter

Abstract: Introduction Preliminary Considerations Parallel, antiparallel, collinear, and noncollinear Characteristic volumina "Classical" spin vectors and spinors The famous spin-orbit interaction Symmetry Considerations Translational invariance Rotational invariance Colloquial or parent lattices Tensorial products of spin and configuration Cell-dependent potentials and exchange fields Magnetic configurations Green's Functions and Multiple Scattering Resolvents and Green's functions The Dyson equation Scaling transformations Integrated density of states Superposition of individual potentials The scattering path operator Angular momentum and partial wave representations Single particle Green's function Symmetry aspects Charge and magnetization densities Changing the orientation of the magnetization Screening transformations The embedded cluster method The Coherent Potential Approximation Configurational averages Restricted ensemble averages The coherent potential approximation The single-site coherent potential approximation Complex lattices and layered systems Remark with respect to systems nanostructured in two dimensions Calculating Magnetic Anisotropy Energies Total energies The magnetic force theorem Magnetic dipole-dipole interactions Exchange and Dzyaloshinskii-Moriya Interactions The free energy and its angular derivatives An intermezzo: classical spin Hamiltonians Relations to relativistic multiple scattering theory The Disordered Local Moment Method (DLM) The relativistic DLM method for layered systems Approximate DLM approaches Spin Dynamics The phenomenological Landau-Lifshitz-Gilbert equation The semiclassical Landau-Lifshitz equation Constrained density functional theory The semiclassical Landau-Lifshitz-Gilbert equation First principles spin dynamics for magnetic systems nanostructured in two dimensions The Multiple Scattering Scheme The quantum mechanical approach Methodological aspects in relation to magnetic anisotropies Physical properties related to magnetic anisotropies Nanostructured in One Dimension: Free and Capped Magnetic Surfaces Reorientation transitions Trilayers, interlayer exchange coupling Temperature dependence A short summary Nanostructured in One Dimension: Spin Valves Interdiffusion at the interfaces Spin valves and noncollinearity Switching energies and the phenomenological Landau-Lifshitz-Gilbert equation Heterojunctions Summary Nanostructured in Two Dimensions: Single Atoms, Finite Clusters, and Wires Finite clusters Finite wires and chains of magnetic atoms Aspects of noncollinearity Nanostructured in Two Dimensions: Nanocontacts, Local Alloys Quantum corrals Magnetic adatoms and surface states Nanocontacts Local alloys Summary A Mesoscopic Excursion: Domain Walls Theory of Electric and Magneto-Optical Properties Linear response theory Kubo equation for independent particles Electric transport-the static limit The Kubo-Greenwood equation Optical transport Electric Properties of Magnetic Nanostructured Matter The bulk anisotropic magnetoresistance (AMR) Current-in-plane (CIP) and the giant magnetoresistance (GMR) Current-perpendicular to the planes of atoms (CPP) Tunneling conditions Spin-valves Heterojunctions Systems nanostructured in two dimensions Domain wall resistivities Summary Magneto-Optical Properties of Magnetic Nanostructured Matter The macroscopic model The importance of the substrate The Kerr effect and interlayer exchange coupling The Kerr effect and magnetic anisotropy energy The Kerr effect in the case of repeated multilayers How surface sensitive is the Kerr effect? Summary Time Dependence Terra incognita Pump-probe experiments Pulsed electric fields Spin currents and torques Instantaneous resolvents and Green's functions Time-dependent multiple scattering Physical effects to be encountered Expectations Afterword Index

Flat band degeneracy and near-zero refractive index materials in acoustic crystals

Abstract: A Dirac-like cone is formed by utilizing the flat bands associated with localized modes in an acoustic crystal (AC) composed of a square array of core-shell-structure cylinders in a water host. Although the triply-degeneracy seems to arise from two almost-overlapping flat bands touching another curved band, the enlarged view of the band structure around the degenerate point reveals that there are actually two linear bands intersecting each other at the Brillouin zone center, with another flat band passing through the same crossing point. The linearity of dispersion relations is achieved by tuning the geometrical parameters of the cylindrical scatterers. A perturbation method is used to not only accurately predict the linear slopes of the dispersions, but also confirm the linearity of the bands from first principles. An effective medium theory based on coherent potential approximation is developed, and it shows that a slab made of the AC carries a near-zero refractive index around the Dirac-like point. Full-wave simulations are performed to unambiguously demonstrate the wave manipulating properties of the AC structures such as perfect transmission, unidirectional transmission and wave front shaping.