Observation of bosonic stimulation in light scattering

TL;DR

This paper demonstrates and analyzes bosonic stimulation in light scattering, showing its dependence on BEC fraction and the effects of interactions, with experimental validation of theoretical predictions.

Contribution

The first experimental observation of bosonic stimulation in light scattering and its theoretical analysis, including the universal bound and dependence on BEC fraction.

Findings

Bosonic enhancement factor is bounded by ζ(2)/ζ(3).

Bosonic stimulation depends linearly on BEC fraction below phase transition.

Bosonic enhancement is reduced in multi-level systems for Raman scattering.

Abstract

For bosons, the transition rate into an already occupied quantum state is enhanced by its occupation number: the effect of bosonic stimulation. Bosonic enhancement of light scattering has been predicted more than 30 years ago but has not been observed before. Here we theoretically investigate and experimentally demonstrate this effect. We show that the bosonic enhancement factor for a harmonically trapped gas is bounded by a universal constant $\zeta(2)/\zeta(3)$ above the phase transition to a Bose-Einstein condensate (BEC), and depends linearly on the BEC fraction just below the phase transition. Bosonically enhanced light scattering is observed and characterized above and below the phase transition, and the effect of interactions is discussed. For a multi-level system, bosonic enhancement is reduced because bosonic stimulation occurs only for Rayleigh scattering, but not for Raman scattering.