Nonperturbative theory of atom-surface interaction: Corrections at short separations

TL;DR

This paper develops a nonperturbative framework for calculating atom-surface interactions at any temperature, revealing significant deviations from traditional Lifshitz theory at very short separations around 1nm.

Contribution

It introduces a nonperturbative approach to atom-surface interactions, extending beyond the standard Lifshitz theory and providing accurate results at nanometer-scale separations.

Findings

Deviations between nonperturbative and perturbative results are significant at about 1nm separation.

Derived simple analytic expressions in classical and ideal-metal limits.

Numerical computations for He* and Na atoms interacting with Au surfaces confirm the theory.

Abstract

The nonperturbative expressions for the free energy and force of interaction between a ground-state atom and a real-material surface at any temperature are presented. The transition to the Matsubara representation is performed, whereupon the comparison is made with the commonly used perturbative results based on the standard Lifshitz theory. It is shown that the Lifshitz formulas for the free energy and force of an atom-surface interaction follow from the nonperturbative ones in the lowest order of the small parameter. Numerical computations of the free energy and force for the atoms of He${}^{\ast}$ and Na interacting with a surface of an Au plate have been performed using the frequency-dependent dielectric permittivity of Au and highly accurate dynamic atomic polarizabilities in the framework of both the nonperturbative and perturbative theories. According to our results, the maximum deviations between the two theories are reached at the shortest atom-surface separations of about 1nm. Simple analytic expressions for the atom-surface free energy are derived in the classical limit and for an ideal-metal plane. In the lowest order of the small parameter, they are foundX// in agreement with the perturbative ones following from the standard Lifshitz theory. Possible applications of the obtained results in the theory of van der Waals adsorption are discussed.