ABSTRACT
Recently, the polaron concept has experienced a renewed interest due to theoretical advances in ultracold quantum gases, quantum information, and high energy physics that will serve as an impetus for future developments in the polaron theory. In this chapter, the authors consider a parabolic confinement potential where rigid interface boundaries are absent and interface-like phonon modes are smoothly distributed in space rather than localized near a sharp boundary and so they examine the electron interaction only with 3D longitudinal polar optical phonons. In the polaron theory, it is necessary to have one unique approach and, in particular, the method of the density matrix in the language of Feynman functional integration is one of them. Over the years the original polaron concept has been generalized to include polarization fields other than the LO-phonon field. The authors examine the bipolaron characteristics in a spherical quantum dot with an all-sided parabolic electronic confinement potential.
