Strong Coupling Polaron in a Slab of Polar Crystal

By using the extensive Pekar's variational method, the strong coupling polaron energy and the effective mass in a slab of polar crystal including both LO- and SO-phonons are derived as a function of the thickness of slab and the coupling constant. When the slab is thin, the SO-phonons not only influence the ground state energy, but also make the polaronic effective mass become non-isotropic.