Eur. Phys. J. D (2012) 66: 321
https://doi.org/10.1140/epjd/e2012-30294-x

Regular Article

Van der Waals–Casimir–Polder interaction of an atom with a composite surface

¹ Physics Department, Ben Gurion University of the Negev, Beer Sheva, Israel
² Institute of Physics and Astronomy, University of Potsdam, Germany

^a e-mail: Carsten.Henkel@physik.uni-potsdam.de

Received: 7 May 2012
Received in final form: 17 July 2012
Published online: 27 December 2012

Abstract

We study the dispersion interaction of the van der Waals and Casimir–Polder (vdW-CP) type between a neutral atom and the surface of a conductor by allowing for nonlocal electrodynamics, i.e. electron diffusion. We consider two models: (i) bulk diffusion, and (ii) diffusion in a surface charge layer. In both cases, we find that the transition to a semiconductor as a function of the conductivity is continuous, unlike the case of a local model. The relevant parameter is the electric screening length and depends on the carrier diffusion constant. We find that for distances comparable to the screening length, vdW-CP data can distinguish between bulk and surface diffusion, hence it can be a sensitive probe for surface states.