Van der Waals dephasing for Dicke subradiance in cold atomic clouds

TL;DR

This paper explores how near-field dipole-dipole interactions affect subradiance in cold atomic clouds, revealing that Van der Waals dephasing reduces cooperative emission lifetimes at higher densities.

Contribution

It demonstrates the impact of vectorial light and near-field effects on subradiance, extending understanding beyond scalar models to more realistic atomic interactions.

Findings

Near-field interactions decrease subradiant lifetimes in dense samples.

Vectorial light considerations reveal detrimental effects absent in scalar models.

Inhomogeneous broadening from near-field effects is analogous to Van der Waals dephasing.

Abstract

We investigate numerically the role of near-field dipole-dipole interactions on the late emission dynamics of large disordered cold atomic samples driven by a weak field. Previous experimental and numerical studies of subradiance in macroscopic samples have focused on low-density samples of pure two-level atoms, without internal structure, which corresponds to a scalar representation of the light. The cooperative nature of the late emission of light is then governed by the resonant optical depth. Here, by considering the vectorial nature of the light, we show the detrimental role of the near-field terms on cooperativity in higher-density samples. The observed reduction in the subradiant lifetimes is interpreted as a signature of the inhomogeneous broadening due to the near-field contributions, in analogy with the Van der Waals dephasing phenomenon for superradiance.