The Abdus Salam International Centre for Theoretical Physics Ground State Energy of a Polaron in a Superlattice

The ground state energy of a polaron in a superlattice was calculated using the doubletime Green functions. The e ective mass of the polaron along the planes perpendicular to the superlattice axis was also calculated. The dependence of the ground state energy and the e ective mass along the planes perpendicular to the superlattice axis on the electron-phonon coupling constant and on the superlattice parameters (i.e. the superlattice period d and the bandwidth ) were studied. It was observed that if an in nite square well potential is assumed, the ground state energy of the polaron decreases (i.e. becomes more negative) with increasing and d, but increases with increasing . For small values of , the polaron ground state energy varies slowly with , becoming approximately constant for large . The e ective mass along the planes perpendicular to the superlattice axis was found to be approximately equal to the mass of an electron for all typical values of , d and .