engleski

Polarons, Bipolarons, and Nonlinear Phonons in the Holstein Model

The Holstein (small polaron) model is studied for an infinite one-dimensional lattice coupled to optical phonons. We consider both ordinary and highly nonlinear phonons. Results are obtained for one electron and for two electrons with on-site Hubbard repulsion. The polaron and bipolaron systems are studied by creating a large, translation-invariant variational space. The variational space contains states that cannot be represented as a product of coherent states. The Hamiltonian is diagonalized exactly (numerically) in the variational space. We calculate the energy and effective mass of a polaron, and the region of stability, binding energy, and mass of the bipolaron. Implications for superconductivity are discussed.

Polarons, Bipolarons

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