Dispersion Interaction between Two Hydrogen Atoms in a Static Electric Field

TL;DR

This paper demonstrates how an external static electric field can significantly alter the dispersion interactions between two hydrogen atoms, enabling control over the force's magnitude and nature, including turning attraction into repulsion.

Contribution

It reveals that external static electric fields can modify and control the dispersion interactions between atoms, including changing their sign and strength, which was not previously established.

Findings

External electric fields can change the space dependence of dispersion forces.

Under certain configurations, dispersion forces can be turned from attractive to repulsive.

The field-induced modifications are significant at typical interatomic distances and achievable field strengths.

Abstract

We consider the dispersion interaction between two ground-state hydrogen atoms, interacting with the quantum electromagnetic field in the vacuum state, in the presence of an external static electric field, both in the nonretarded and in the retarded Casimir-Polder regime. We show that the presence of the external field strongly modifies the dispersion interaction between the atoms, changing its space dependence. Moreover, we find that, for specific geometrical configurations of the two atoms with respect to the external field and/or the relative orientation of the fields acting on the two atoms, it is possible to change the character of the dispersion force, turning it from attractive to repulsive, or even make it vanishing. This new finding clearly shows the possibility to control and tailor interatomic dispersion interactions through external actions. By a numerical estimate of the field-modified interaction, we show that at typical interatomic distances the change of the interaction's strength can match or even outmatch the unperturbed interaction; this can be obtained for values of the external field that can be currently achieved in the laboratory, and sufficiently weak to be taken into account perturbatively.