2024-03-29T01:14:43Z
https://niigata-u.repo.nii.ac.jp/oai
oai:niigata-u.repo.nii.ac.jp:00002256
2022-12-15T03:35:08Z
176:488:489
453:454
A Possible Bipolaronic Transition in β-pyrochlore Compounds
A Possible Bipolaronic Transition in β-pyrochlore Compounds
Fuse, T.
7659
Ono, Y.
62
β-Pyrochlore oxide
KOs2O6
Bipolaronic transition
Hubbard–Holstein model
We investigate the Hubbard–Holstein model by using the dynamical mean-field theory combined with the exact diagonalization method. Below a critical temperature Tcr, a coexistence of two solutions, small lattice fluctuating solution (polaronic state) and large one (bipolaronic state), is found for the same value of the electron–phonon coupling g in the range gc1<g<gc2 for a fixed value of the Coulomb interaction U. As the result, the system shows a first-order phase transition at Tp(<T cr) from the bipolaronic to the polaronic states as T decreases. The effective potential for oscillating atoms, which is renormalized due to the effect of g, is double-well type for T>Tp, while it is single-well type for T<Tp. The obtained transition for small U case with small Tp and discontinuities in physical quantities seems to be account for the rattling transition observed in the β-pyrochlore oxide KOs2O6.
journal article
Elsevier
2010-12
application/pdf
Physica. C, Superconductivity and its applications
Supplement 1
470
S701
S702
Physica. C, Superconductivity and its applications
AA11461984
09214534
https://niigata-u.repo.nii.ac.jp/record/2256/files/980.pdf
eng
info:doi/10.1016/j.physc.2010.01.022