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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: In this article, a diagrammatical analysis of a previously reported set of approximations for the averaged electronic resolvent (z − H]−1 ) in substitutional alloys is made.
Abstract: A diagrammatical analysis of a previously reported set of approximations for the averaged electronic resolvent 〈[z - H]−1〉 in substitutional alloys is made. The results are found to be in correspondence with applicability of the method revealed in a numerical analysis beyond the coherent potential approximation. A new modification of the method is suggested which is free of shortcomings of the original version. It enables relatively very easy and in principle almost exact computer calculations of spectra of substitutional alloys, at least for simplest model Hamiltonians. A simple numerical example is solved.
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9 citations
TL;DR: In this paper, the authors present a theoretical formalism to calculate the configuration averaged time-dependent current flowing through a phase coherent device containing disorder sites where the transient current is driven by sharply turning on and off the external bias voltage.
Abstract: Predicting time-dependent quantum transport in the transient regime is important for understanding the intrinsic dynamic response of a nanodevice and for predicting the limit of how such a device can switch on or off a current. Theoretically, this problem becomes quite difficult to solve when the nanodevice contains disorder because the calculated transient current must be averaged over many disorder configurations. In this work, we present a theoretical formalism to calculate the configuration averaged time-dependent current flowing through a phase coherent device containing disorder sites where the transient current is driven by sharply turning on and off the external bias voltage. Our theory is based on the Keldysh nonequilibrium Green's function (NEGF) formalism and is applicable in the far from equilibrium nonlinear response quantum transport regime. The effects of disorder scattering are dealt with by the coherent potential approximation (CPA) extended in the time domain. We show that after approximations such as CPA and vertex corrections for calculating the multiple impurity scattering in the transient regime, the derived NEGFs perfectly satisfy a Ward identity. The theory is quantitatively verified by comparing its predictions to the exact solution for a tight-binding model of a disordered two-probe transport junction.
9 citations
TL;DR: In this article, a general and compact scheme was presented to calculate the self-energy of an electron in disordered alloys and the effect of atomic correlation was taken into account in a systematic way.
Abstract: A general and compact scheme is presented to calculate the self-energy of an electron in disordered alloys. The effect of atomic correlation is taken into account in a systematic way.
9 citations
TL;DR: In this paper, the structure of polycrystalline Ni0.5Zn0.4 ferrites was measured using an X-ray diffractometer (XRD) and the magnetic properties of the samples were tested at room temperature by a superconducting quantum interference device (SQUID).
Abstract: Polycrystalline Ni0.5Zn0.5Fe2O4 ferrites have been prepared using the solid-state reaction technique. The structure of ferrite was measured using an X-ray diffractometer (XRD). It is shown that the structure of Ni0.5Zn0.5Fe2O4 ferrites is a single spinel structure. The magnetic properties of the samples were tested at room temperature by a superconducting quantum interference device (SQUID) to determine magnetic properties versus temperature and applied magnetic field. Based on first-principles spin-density functional calculations, using the Korringa–Kohn–Rostoker method (KKR) combined with the coherent potential approximation (CPA), the ferromagnetic and half-metallic behaviors was observed with LDA (local density approximation) and LDA–SIC (local density approximation-self-interaction correction) approximation.
9 citations
TL;DR: Experimental band topography is compared to the calculations using the methods of Korringa-Kohn-Rostoker with the coherent potential approximation (CPA) and the linearized augmented plane wave with local orbitals (LAPW+LO) method, which indicate that at least one of the hole pockets has a two-dimensional character.
Abstract: The electronic structure of superconducting Fe1:03Te0:94S0:06 has been studied by angle-resolved photoemission spectroscopy (ARPES). Experimental band topography is compared to the calculations using the methods of Korringa‐Kohn‐Rostoker (KKR) with the coherent potential approximation (CPA) and the linearized augmented plane wave with local orbitals (LAPWC LO) method. The region of the0 point exhibits two hole pockets and a quasiparticle peak close to the chemical potential ( ) with undetectable dispersion. This flat band with mainly d z 2 orbital character is most likely formed by the top of the outer hole pocket or is evidence of a third hole band. It may cover up to 3% of the Brillouin zone volume and should give rise to a Van Hove singularity. Studies performed for various photon energies indicate that at least one of the hole pockets has a two-dimensional character. The apparently nondispersing peak at is clearly visible for 40 eV and higher photon energies, due to an effect of the photoionization cross-section rather than band dimensionality. Orbital characters calculated by LAPWC LO for stoichiometric FeTe do not reveal the flat dz2 band but are in agreement with the experiment for the other dispersions around0 in Fe1:03Te0:94S0:06. (Some figures may appear in colour only in the online journal)
9 citations