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Register a new userProperties of Many-Polaron in Fractional Dimensional Space
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Added by
Krushnamohan Mohapatra Mr
Publication date
2014
fields
Physics
and research's language is
English
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Polaron binding energy and effective mass are calculated in the fractional-dimensional space approach using the second-order perturbation theory. The effect of carrier density on the static screening correction of the electron-phonon interaction is calculated using the Hubbards local field factor. It is found that the effective mass and the binding energy both decrease with increase in doping.
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Exact results for the density of states and the ac conductivity of the spinless Holstein model at finite carrier density are obtained combining Lanczos and kernel polynomial methods.
The cross over from low to high carrier densities in a many-polaron system is studied in the framework of the one-dimensional spinless Holstein model, using unbiased numerical methods. Combining a novel quantum Monte Carlo approach and exact diagonalization, accurate results for the single-particle spectrum and the electronic kinetic energy on fairly large systems are obtained. A detailed investigation of the quality of the Monte Carlo data is presented. In the physically most important adiabatic intermediate electron-phonon coupling regime, for which no analytical results are available, we observe a dissociation of polarons with increasing band filling, leading to normal metallic behavior, while for parameters favoring small polarons, no such density-driven changes occur. The present work points towards the inadequacy of single-polaron theories for a number of polaronic materials such as the manganites.
The carrier-density dependence of the photoemission spectrum of the Holstein many-polaron model is studied using cluster perturbation theory combined with an improved cluster diagonalization by Chebychev expansion.
The polaron binding energy and effective mass in a degenerate polar gas is calculated in the fractional-dimensional approach under plasmon pole approximation.The effect of carrier densities on the static and dynamic screening correction of the electron-phonon interaction and electron-electron interaction to the polaronic propertis is calculated from electron self-energies within the second-order perturbation method. The Hubbard local field factor has been used for the static screening correction in the polaronic properties. We found that polaronic properties decrease with increase with carrier density and dimensionality of the system.
We show that in crystals where light ions are symmetrically intercalated between heavy ions, the electron-phonon coupling for carriers located at the light sites cannot be described by a Holstein model. We introduce the double-well electron-phonon coupling model to describe the most interesting parameter regime in such systems, and study it in the single carrier limit using the momentum average approximation. For sufficiently strong coupling, a small polaron with a robust phonon cloud appears at low energies. While some of its properties are similar to those of a Holstein polaron, we highlight some crucial differences. These prove that the physics of the double-well electron-phonon coupling model cannot be reproduced with a linear Holstein model.
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