Importance of nonlocal effects for the evaluation of static screening at a Au surface from ellipsometry

Abstract

It is shown that local optics fails when used to explain the ellipsometry experiment of Chao and Costa, and is responsible for the wrong conclusion that the mean penetration depth of the electric field into the metal increases linearly with the charge induced at the metal surface. Using instead the hydrodynamic approximation as the simplest version of nonlocal optics and a model, simulating the region of low electron density at the surface, it is found that the mean penetration depth is nearly independent of the surface charge, in agreement with previous results of electroreflectance studies and microscopical calculations.