Variational path-integral treatment of a translation invariant   many-polaron system
  A translation invariant N-polaron system is investigated at arbitrary electron-phonon coupling strength, using a variational principle for path integrals for identical particles. An upper bound for the ground state energy is found as a function of the number of spin up and spin down polarons, taking the electron-electron interaction and the Fermi statistics into account. The resulting addition energies and the criteria for multipolaron formation are discussed. 
F. Brosens (1), S. N. Klimin (1,2), and J. T. Devreese (1) ((1) TFVS,   Universiteit Antwerpen,(2) FSM, Universitatea de Sta...