Ab initio calculation of the reflectance anisotropy of GaAs (110): the role of nonlocal polarizability and local fields

We demonstrate that the description of the optical reflectance anisotropy of GaAs(110) requires a complete microscopic treatment of both surface and bulk, which is feasible in the discrete cellular method. This method is an extension of standard discrete dipole calculations and accounts for non-locality in the electro-dynamical and quantum-mechanical interactions through the use of both real space local fields and ab-initio nonlocal polarizabilities. The results of our calculations are in excellent agreement with experiment and we show that the anisotropy is surface induced.