  The term "surface polarization" is introduced to describe the in-plane
polarization existing at the surface of an insulating crystal when the in-plane
surface inversion symmetry is broken. Here, the surface polarization is
formulated in terms of a Berry phase, with the hybrid Wannier representation
providing a natural basis for study of this effect. Tight binding models are
used to demonstrate how the surface polarization reveals itself via the
accumulation of charges at the corners/edges for a two dimensional rectangular
lattice and for GaAs.
