Ground state energy of a polaron in a superlattice

The ground state energy of a polaron in a superlattice was calculated using the double-time Green functions. The effective mass of the polaron along the planes perpendicular to the superlattice axis was also calculated. The dependence of the ground state energy and the effective mass along the planes perpendicular to the superlattice axis on the electron-phonon coupling constant alpha, and on the superlattice parameters (i.e. the superlattice period d and the bandwidth Delta) were studied. It was observed that if an infinite square-well potential is assumed, the ground state energy of the polaron decreases (i.e. becomes more negative) with increasing alpha and d, but increases with increasing Delta. For small values of alpha, the polaron ground state energy varies slowly with a, becoming approximately constant for large Delta. The effective 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 alpha, d and Delta. (C) 2001 Academic Press.