Physics – Condensed Matter – Strongly Correlated Electrons
Scientific paper
2000-04-25
Physica D (1998) vol.113 pp.307-317
Physics
Condensed Matter
Strongly Correlated Electrons
Scientific paper
10.1016/S0167-2789(97)00283-2
The bound states of two electrons in the adiabatic Holstein-Hubbard model are studied numerically in one and two dimensions from the anticontinuous limit. This model involves a competition between a local electron-phonon coupling (with a classical lattice) which tends to form pairs of electrons and the repulsive Hubbard interaction $U \geq 0$ which tends to break them. In 1D, the ground-state always consists in a pair of localized polarons in a singlet state. They are located at the same site for U=0. Increasing U, there is a first order transition at which the bipolaron becomes a spin singlet pair of two polarons bounded by a magnetic interaction. The pinning mode of the bipolaron soften in the vicinity of this transition leading to a higher mobility of the bipolaron which is tested numerically. In 2D, and for any $U$, the electron-phonon coupling needs to be large enough in order to form small polarons or bipolarons instead of extended electrons. We calculate the phase diagram of the bipolaron involving first order transitions lines with a triple point. A pair of polarons can form three types of bipolarons: a) on a single site at small $U$, b) a spin singlet state on two nearest neighbor sites for larger $U$ as in 1D and c) a new intermediate state obtained as the resonant combination of four 2-sites singlet states sharing a central site, called quadrisinglet. The breathing and pinning internal modes of bipolarons in 2D generally only weakly soften and thus, they are practically not mobile. On the opposite, in the vicinity of the triple point involving the quadrisinglet, both modes exhibit a significant softening. However, it was not sufficient for allowing the existence of a classical mobile bipolaron (at least in that model).
Aubry Serge
Proville Laurent
No associations
LandOfFree
Mobile Bipolarons in the Adiabatic Holstein-Hubbard Model in 1 and 2 dimensions does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Mobile Bipolarons in the Adiabatic Holstein-Hubbard Model in 1 and 2 dimensions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mobile Bipolarons in the Adiabatic Holstein-Hubbard Model in 1 and 2 dimensions will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-473587