Effect of superradiance on transport of diffusing photons in cold atomic gases

TL;DR

This paper investigates how superradiance influences photon transport in cold atomic gases, revealing a long-range $1/r$ potential between atoms that affects scattering properties and can be observed under specific experimental conditions.

Contribution

It introduces the concept that superradiance induces a $1/r$ potential affecting photon scattering, a novel insight into cooperative atomic effects on light transport.

Findings

Superradiance creates an attractive $1/r$ potential between atoms.

Superradiant pairs alter photon mean free path and group velocity.

Conditions for observing these effects are discussed and compared with experiments.

Abstract

We show that in atomic gases cooperative effects like superradiance and subradiance lead to a potential between two atoms that decays like $1/r$. In the case of superradiance, this potential is attractive for close enough atoms and can be interpreted as a coherent mesoscopic effect. The contribution of superradiant pairs to multiple scattering properties of a dilute gas, such as photon elastic mean free path and group velocity, is significantly different from that of independent atoms. We discuss the conditions under which these effects may be observed and compare our results to recent experiments on photon transport in cold atomic gases.