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.

Mean-field approach for Anderson-type off-diagonal disorder

Abstract: We report a generalized auxiliary coherent medium theory to settle the longstanding challenge of Anderson-type off-diagonal disorder (AODD) for simulating disordered alloys. The AODD is transformed into a diagonal-like disorder with a weighted discrete distribution in an auxiliary medium. This approach is demonstrated for simulating the phonon spectral in NiFe and NiPt alloys, and it is found that accounting for AODD substantially enhances the phonon linewidth to agree well with the supercell and experimental results, compared to results with averaged-value ODD. This paper provides an effective approach to treat the large fluctuation in ODD in disordered materials, presenting an important progress for mean-field simulations in the embedding framework.

Excitonic polaron in the molecular crystal model: Nonlocal dynamic coherent-potential approximation

Abstract: A nonlocal dynamic coherent-potential approximation is formulated as a further development of the dynamic coherent-potential method. The nonlocal dynamic coherent-potential approximation is an efficient method of determining the one-exciton Green’s function in a model with the Hamiltonian in the strong-coupling approximation, where a spectrum of optical phonons is assumed, and the exciton-phonon interaction operator is linear or quadratic in the phonon operators. A system of recursion equations is derived, from which the coherent potential is found as a function of the energy E and the wave vector k. An analytical expression is derived for the one-exciton Green’s function in the case of narrow (in comparison with the phonon energy) exciton bands and exciton-phonon interaction linear in the phonon operators. For broader exciton bands and more complex exciton-phonon interaction the system of equations determining the coherent potential represents a recursion algorithm, which can be effectively implemented by numerical means.

CPA Theory of Superconducting Alloys with Diagonal and Off-Diagonal Disorder

Abstract: The general theory of disorder in superconducting alloys was discussed We use standard Wannier function representation and allow for diagonal and ofi-diagonal disorder We generalized the coherent potential approximation in the version able to deal with ofi-diagonal disorder in normal systems to treat superconducting state As an illustration we calculate the quasiparticle density of states and gap function of a d-wave superconductor We show inter alia that the rate at which superconductivity disappears depends on the kind of disorder and for ofi-diagonal disorder it depends on the details of its realization

Electronic Structure of Disordered Binary Alloys: α-Brass

Abstract: We have given a brief review of the existing approaches towards the study of the electronic structure of disordered binary alloys and have discussed Soven's single-site coherent potential approximation. An angular momentum representation of the Green function with Slater's δ-function-type potential is used to calculate the spectral density of electronic states of the disordered alloy, α-brass. We have compared the results of our calculation with available optical and photoemission data.

Atomic disorder scattering in emerging transistors by parameter-free first principle modeling

Abstract: A parameter-free first principle modeling methodology is reported with emphasis on simulating effects of atomistic disorder in nano-scale transistors. The technique is based on the developed theory of nonequilibrium coherent potential approximation and a linear scaling sparse Hamiltonian implementation. Using this technique, effects of disorder scattering to the quantum transport properties of a boron-nitrogen (B-N) co-doped graphene tunnel field effect transistor (TFET) is investigated.