Bipolaron in a quasi-0D quantum dot

• Published in: Superlattices and microstructures 2008, Vol.43 (1), p.44-52
• Main Authors: Fai, L.C., Fomethe, A., Fotue, A.J., Mborong, V.B., Domngang, S., Issofa, N., Tchoffo, M.
• Format: Article
• Language: English
• Subjects: Bipolaron; Coulomb-coupling constant; Coupling energy; Fröhlich electron–phonon coupling constant; Parabolic confinement; Polaron; Quantum dot; Self-action potential
• ISSN: 0749-6036; 1096-3677
• DOI: 10.1016/j.spmi.2007.05.003

Bipolaron states in a quasi-0D quantum dot with a spherical parabolic confinement potential are investigated by applying the Feynman variational principle. The bipolaron coupling energy and self-action potential energy are found to increase with an increase in the Fröhlich electron–phonon-coupling constant. There is also a non-monotonic dependence of the bipolaron coupling energy on the quantum dot radius. With decreasing structure radius the bipolaron coupling energy increases. However, from a critical radius it starts decreasing as the radius decreases, due to the dominance of the coulomb-to-phonon mediated interaction. When electrons in the bipolaron are forcefully neighboured, the polarization of the structure is intensified and consequently there is Coulomb repulsion. The possibility of bipolaron formation depends on the strength of the direct Coulomb repulsion which, in turn, depends on the quantum dot radius. The main contribution to the bipolaron coupling energy comes from the self-action potential. This self-action potential energy influences the energy state of the bipolaron considerably. The ratio of optical-to-static dielectric constants significantly affects the bipolaron coupling energy.