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.

Collective excitations in a planar model of a classical spin glass

Abstract: The authors have extended earlier numerical investigations of the harmonic collective excitations in the Edwards-Anderson model (1976) of a planar spin glass to one and two dimensions. In two dimensions, as in three, low-frequency excitations propagate modes with a linear dispersion law. They outline a theoretical analysis based on the coherent potential approximation (CPA) which reproduces the spin-wave velocities that were inferred from the numerical work. In one dimension the CPA accounts for the density of states and the dynamic structure factor over the entire zone except possibly at very long wavelengths where a non-linear dispersion law is predicted.

Coherent-potential-approximation study of excitonic absorption in orientationally disordered molecular aggregates

Abstract: We study the dynamics of a single Frenkel exciton in a disordered molecular chain. The coherent-potential approximation is applied to the situation where the single-molecule excitation energies as well as the transition dipole moments, both their absolute values and orientations, are random. Such a model is believed to be relevant for the description of the linear optical properties of one-dimensional J aggregates. We calculate the exciton density of states, the linear absorption spectra, and the exciton coherence length which reveals itself in the linear optics. A detailed analysis of the low-disorder limit of the theory is presented. In particular, we derive asymptotic formulas relating the absorption linewidth and the exciton coherence length to the strength of disorder. Such expressions account simultaneously for all the above types of disorders and reduce to well-established form when no disorder in the transition dipoles is present. The theory is applied to the case of purely orientational disorder and is shown to agree well with exact numerical diagonalization.

Calculation of physical quantities in α-SiHx

Abstract: A simple model of α-SiHx is studied; its only adjustable parameter is the hydrogen concentration x. By combining the coherent potential approximation with the potential well analogy explicit results are obtained for quantities such as optical absorption, position of mobility edges, mean free path, density of states at the mobility edge, and pre-exponential factor in the dc conductivity. The latter is obtained by neglecting the effects of electron-phonon interaction, which is expected to lead to a strongly temperature-dependent mobility. The theoretical results are in reasonable agreement with experimental data.

Coherent potential approach to exchange-induced band splitting in diluted magnetic semiconductors under a saturating magnetic field

Abstract: Applying the coherent potential approximation (CPA) to a model which describes magnetic and chemical disorder in an AII1-xMnxBVI-type diluted magnetic semiconductor (DMS) with a strong applied magnetic field, we calculate the band-edge energy shift as a function of the Mn concentration (x) The effects of the band offset and exchange interaction on the extended carrier state in a DMS are studied systematically The apparent enhancement of the p-d exchange interaction which is observed in Cd1-xMnxS is explained well as a multiple-scattering effect which is significant for small x in disordered systems The dominant origin is not a large attractive chemical potential at the Mn site, but a large exchange energy relative to the bandwidth