Magnetic Field Enhanced Coherence Length in Cold Atomic Gases

TL;DR

This paper demonstrates that applying an external magnetic field to cold rubidium gases can increase the coherence length of light scattering, contrary to typical expectations, by lifting Zeeman degeneracy and enhancing backscattering coherence.

Contribution

It provides experimental evidence and theoretical modeling showing magnetic fields can enhance coherence length in cold atomic gases, a novel insight in light scattering studies.

Findings

Magnetic field increases backscattering enhancement factor.

Good agreement between experiment and Monte Carlo simulation.

Coherence length can be increased by magnetic field due to Zeeman degeneracy lifting.

Abstract

We study the effect of an external magnetic field on coherent backscattering of light from a cool rubidium vapor. We observe that the backscattering enhancement factor can be {\it increased} with $B$. This surprising behavior shows that the coherence length of the system can be increased by applying a magnetic field, in sharp contrast with ususal situations. This is mainly due to the lifting of the degeneracy between Zeeman sublevels. We find good agreement between our experimental data and a full Monte-Carlosimulation, taking into account the magneto-optical effects and the geometry of the atomic cloud.