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      Effect of screening of the electron-phonon interaction on mass renormalization and optical conductivity of the Extended Holstein model polarons

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          Abstract

          An interacting electron-phonon system is considered within the Extended Holstein model at strong coupling regime and nonadiabatic approximation. It is assumed that screening of an electron-phonon interaction is due to the excess electrons in a lattice. An influence of the screening on the mass and optical conductivity of a lattice polarons is studied. A more general form Yukawa-type electron-phonon interaction potential potential is accepted and corresponding forces are derived in a lattice. It is emphasized that the screening effect is more pronounced at the values of screening radius comparable with a lattice constant. It is shown that the mass of a lattice polaron obtained using Yukawa-type electron-phonon interaction potential is less renormalized than those of the early studied works at the same screening regime. Optical conductivity of lattice polarons is calculated at different screening regimes. The screening lowers the value of energy that corresponds to the peak of the optical conductivity curve. The shift (lowering) is more pronounced at small values of screening radius too. The factors that give rise to this shift is briefly discussed.

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          Polaron contribution to the infrared optical response ofLa2−xSrxCuO4+δandLa2−xSrxNiO4+δ

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            Mobile small polaron

            Extending the Froehlich polaron problem to a discrete ionic lattice we study a polaronic state with a small radius of the wave function but a large size of the lattice distortion. We calculate the energy dispersion and the effective mass of the polaron with the 1/\lambda perturbation theory and with the exact Monte Carlo method in the nonadiabatic and adiabatic regimes, respectively. The ``small'' Froehlich polaron is found to be lighter than the small Holstein polaron by one or more orders of magnitude.
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              Bipolarons in the Extended Holstein Hubbard Model

              We numerically and analytically calculate the properties of the bipolaron in an extended Hubbard Holstein model, which has a longer range electron-phonon coupling like the Fr\" ohlich model. In the strong coupling regime, the effective mass of the bipolaron in the extended model is much smaller than the Holstein bipolaron mass. In contrast to the Holstein bipolaron, the bipolaron in the extended model has a lower binding energy and remains bound with substantial binding energy even in the large-U limit. In comparison with the Holstein model where only a singlet bipolaron is bound, in the extended Holstein model a triplet bipolaron can also form a bound state. We discuss the possibility of phase separation in the case of finite electron doping.
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                Author and article information

                Journal
                10 August 2013
                Article
                10.1140/epjb/e2010-00163-9
                1308.2312
                95caf139-1862-4590-af0f-80e9f122fc7d

                http://arxiv.org/licenses/nonexclusive-distrib/1.0/

                History
                Custom metadata
                Eur. Phys. Jour. B, vol. 75, issue 4, pp. 481-488 (2010)
                8 pages, 10 figures, 1 table. arXiv admin note: substantial text overlap with arXiv:1308.2197
                cond-mat.str-el

                Condensed matter
                Condensed matter

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