Monodeep Chakraborty, Masaki Tezuka, B. I. Min
Employing the recently developed self-consistent variational basis generation scheme, we have investigated the bipolaron-bipolaron interaction within the purview of Holstein-Hubbard and the Froehlich-Hubbard model on a discrete one-dimensional lattice. The density-matrix renormalization group (DMRG) method has also been used for the Holstein-Hubbard model. We have shown that there exists no bipolaron-bipolaron attraction in the Holstein-Hubbard model. In contrast, we have obtained clear-cut bipolaron-bipolaron attraction in the Froehlich-Hubbard model. Composite bipolarons are formed above a critical electron-phonon coupling strength, which can survive the finite Hubbard U effect. We have constructed the phase diagram of Froehlich-Hubbard polarons and bipolarons, and discussed the phase separation in terms of the formation of composite bipolarons.
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http://arxiv.org/abs/1306.4751
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