Strong-coupling analysis of large bipolarons in 2 and 3 dimensionsStrong-coupling analysis of large bipolarons in 2 and 3 dimensions
Faculty of Sciences. Physics

Faculty of Social Sciences. Sociology

Condensed Matter Theory

Department of Physics

Theory of quantum systems and complex systems

article

1992Lancaster, Pa, 1992

Physics

Physical review : B : condensed matter and materials physics. - Lancaster, Pa, 1998 - 2015

45(1992):10, p. 5262-5269

1098-0121

1550-235X

A1992HJ68900016

E

English (eng)

University of Antwerp

In the limit of strong electron-phonon coupling, we use either a Pekar-type or an oscillator wave function for the center-of-mass coordinate and either a Coulomb or an oscillator wave function for the relative coordinate, and are able to reproduce all the results from the literature for the large-bipolaron binding energy. Lower bounds are constructed for the critical ratio eta(c) of dielectric constants below which bipolarons can exist. It is found that, in the strong-coupling limit, the stability region for bipolaron formation is much larger in two dimensions (2D) than in 3D. We introduce a model that combines the averaging of the relative coordinate over the asymptotically best wave function with a path-integral treatment of the center-of-mass motion. The stability region for bipolaron formation is increased compared with the full path-integral treatment at large values of the coupling constant alpha. The critical values are alpha(c) almost-equal-to 9.3 in 3D and alpha(c) almost-equal-to 4.5 in 2D. Phase diagrams for the presented models are also obtained in both 2D and 3D.

https://repository.uantwerpen.be/docman/irua/8d12f4/4913.pdf

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