A Green's-function equation-of-motion analysis of the large polaron is presented. Existing theories for the ground-state energy and effective mass are obtained from a nondiagonal form of the Fock approximation to the electron self-energy. A connection between the usual canonical transformation techniques and the Green's-function approach is given explicitly. The effects of vertex corrections and translational invariance are examined in the context of these results.

• Received 18 November 1970

DOI:https://doi.org/10.1103/PhysRevB.3.3487