Nonreciprocal and nonconservative forces on binary systems of identical atoms

TL;DR

This paper investigates the dynamics, emission, and internal forces of a two-atom system, revealing nonreciprocal forces that can cause measurable displacements, with implications for understanding atomic interactions.

Contribution

It provides closed-form expressions for the system's evolution, emission patterns, and internal forces, highlighting nonreciprocal and nonconservative effects in identical atom pairs.

Findings

Nonreciprocal forces induce net oscillatory forces.

Estimated atomic displacement can reach 120 nm.

Derived explicit formulas for system dynamics and emission.

Abstract

The dynamical and radiative features of an excited system of two identical atoms are analysed. The metastability of the system, the directionality of its emission and its internal forces are studied. Closed-form expressions are derived for the time-evolution of the system, for the angular distribution of its spontaneous emission, and for its internal dipole forces, both conservative and nonconservative. The latter reveals the presence of nonreciprocal forces, which leads to a net oscillatory force upon the system. We estimate that, for a free binary system of Li Rydberg atoms, the net internal force may cause a displacement of its center of mass as large as $120 nm$ over a lifetime.