Dephasing in an atom

When an atom in vacuum is near the surface of a dielectric the energy of a fluctuating electromagnetic field depends on a distance between them resulting, as known, in a force called van der Waals. Besides this fluctuation phenomenon there is one associated with formation of a mean electric field, which is equivalent to an order parameter. In this case atomic electrons are localized within atomic distances close to the atom and the total ground state energy is larger, compared to the bare atom, due to the polarization of the dielectric and the creation of a mean electric field locally distributed in the dielectric. The phenomenon differs from the usual ferroelectricity and has a pure quantum origin. This results in (i) an unusual atom-dielectric force different from the van der Waals one and (ii) an anomalous Lamb shift in the atom.