https://doi.org/10.1140/epjb/e2012-21079-2
Regular Article
Bipolarons and polarons in the Holstein-Hubbard model: analogies and differences
1
Institute of Physics, Bijenička c. 46, 10000
Zagreb,
Croatia
2
Department of Physics, Faculty of Science, University of
Zagreb, Bijenička c.
32, 10000
Zagreb,
Croatia
a e-mail: obarisic@ifs.hr
Received:
27
December
2011
Received in final form:
1
February
2012
Published online:
30
March
2012
The single bipolaron problem is examined in the context of the 1D Holstein-Hubbard model, emphasizing analogies and differences with respect to the complementary single polaron physics. The bipolaron band structure below the phonon threshold is revealed, showing a complex relationship between numerous excited bands as the adiabatic limit is approached. Light bipolarons with significant binding energy, the stability of large bipolarons, the small to large bipolaron crossover as a function of the Hubbard repulsion, as well as the bipolaron dissociation, are investigated in detail, disentangling adiabatic, nonadiabatic and lattice coarsening effects. It is emphasized that condensation of bipolarons occurs in the dilute limit only at very low temperatures.
Key words: Solid State and Materials
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag, 2012