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Singlet and triplet bipolarons on the triangular lattice

Hague, J. P; Kornilovitch, P. E.; Samson, J. H. and Alexandrov, A. S. (2008). Singlet and triplet bipolarons on the triangular lattice. Journal of Physics and Chemistry of Solids, 69(12) pp. 3304–3306.

DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1016/j.jpcs.2008.06.129
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Abstract

We study the Coulomb–Fröhlich model on a triangular lattice, looking in particular at states with angular momentum. We examine a simplified model of crab bipolarons with angular momentum by projecting onto the low energy subspace of the Coulomb–Fröhlich model with large phonon frequency. Such a projection is consistent with large long-range electron–phonon coupling and large repulsive Hubbard U. Significant differences are found between the band structure of singlet and triplet states: The triplet state (which has a flat band) is found to be significantly heavier than the singlet state (which has mass similar to the polaron). We test whether the heavier triplet states persist to lower electron–phonon coupling using continuous time quantum Monte Carlo (QMC) simulation. The triplet state is both heavier and larger, demonstrating that the heavier mass is due to quantum interference effects on the motion. We also find that retardation effects reduce the differences between singlet and triplet states, since they reintroduce second order terms in the hopping into the inverse effective mass.

Item Type: Journal Article
ISSN: 0022-3697
Keywords: A. Oxides; D. Superconductivity; D. Electronic structure; D. Transport properties; D. Phonons
Academic Unit/Department: Science > Physical Sciences
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Biomedical Research Network (BRN)
Item ID: 12296
Depositing User: James Hague
Date Deposited: 27 Jan 2009 02:21
Last Modified: 07 Mar 2014 13:49
URI: http://oro.open.ac.uk/id/eprint/12296
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