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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.
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TL;DR: The response of a biased double-barrier quantum well to a small ac voltage with characteristic time τ resp and the transit or dwell time τ trans are calculated using nonequilibrium Green's-function techniques.
Abstract: The response of a biased double-barrier quantum well to a small ac voltage with characteristic time τ resp and the transit or dwell time τ trans are calculated using nonequilibrium Green's-function techniques. The tunneling process is shown to be predominantly sequential for an In x Ga 1-x As/In y Al 1-y As structure due to only well alloy scattering treated in the coherent-potential approximation
24 citations
TL;DR: In this paper, the density of states in the two-dimensional white noise problem is calculated from the coherent potential approximation at high energy and from fluctuation theory at low energies; both the exponent and the power of E in the prefactor for density of fluctuation states are evaluated.
Abstract: The density of states in the two-dimensional white noise problem is calculated from the coherent potential approximation at high energy and from fluctuation theory at low energies; both the exponent and the power of E in the prefactor for the density of fluctuation states are evaluated. Comparison is made with the results of a tight binding simulation of the white noise problem, and good agreement between theory and calculation is obtained. Calculation of the conductivity of different sized samples enables the mobility edge to be determined, and it is found that the critical value of g=n(Ec)/n0 is more than 0.8, in contrast with much lower values suggested earlier. The metallic conductivity is compared with the CPA result, and found to be lower by a factor of 0.4. Some modifications are introduced into the theory when account is taken of orbital degeneracy. Comparison is made with Pollitt's experiments on the inversion layer.
23 citations
TL;DR: In this paper, the influence of both spin fluctuations and impurity potential on conduction electrons is described in a coherent potential approximation, which coincides in the limit of zero-impurity potential.
Abstract: We study the ferromagnetic transition in a three-dimensional double-exchange model containing impurities. The influence of both spin fluctuations and the impurity potential on conduction electrons is described in a coherent potential approximation. In the framework of the thermodynamic approach we construct a Landau functional for the system ``electrons (in disordered environment) + core spins.'' Analyzing the Landau functional we calculate the temperature of the ferromagnetic transition ${T}_{C}$ and paramagnetic susceptibility \ensuremath{\chi}. For ${T}_{C},$ we thus extend the result obtained by Furukawa in the framework of the dynamical mean-field approximation, with which our result coincides in the limit of zero-impurity potential. We find that alloy disorder, able to produce a gap in the density of electron states, can substantially decrease ${T}_{C}$ with respect to the case of no impurities.
23 citations
TL;DR: In this article, a new approximation based on treating, self-consistently, clusters of sites is introduced to describe the details of the energy spectrum of a disordered alloy when the mean free path is short.
23 citations
TL;DR: In this article, first principle calculations using supercell approach and coherent potential approximation (CPA) are performed to investigate the electronic and magnetic structures of Fe3−xMnxSi and Fe3-yMnSiy alloys, where x,y=0, 0.25, and 0.75 with a small direct band gap that increases for higher concentrations of Mn.
Abstract: First principle calculations using supercell approach and coherent potential approximation (CPA) are performed to investigate the electronic and magnetic structures of Fe3−xMnxSi and Fe3−yMnSiy alloys, where x,y=0, 0.25, 0.50, 0.75, 1.00, 1.25, 1.5, 1.75, and 2.25. Using supercell calculations we obtained a metallic behavior for x=0, 0.25, and 0.5 in Fe3−xMnxSi alloys with spin polarizations of 24%, 39%, and 93%, respectively. The behavior starts to be half-metallic at x=0.75 with a small direct band gap that increases for higher concentrations of Mn. Among the half-metallic systems, only those of L21 structure at x=1 and 2 possess indirect band gaps along Γ-X symmetry line. The change of Si concentration in Fe3−yMnSiy structures retrieve the metallic behavior for all concentrations except y=1.25 that shows a half-metallic behavior with a direct band gap of 0.27 eV. We obtained a good agreement between supercell and CPA calculations for the values of the magnetic moment and the trends of the formation ene...
23 citations