Quantum interference-enhanced deep sub-Doppler cooling of 39 K atoms in gray molasses

TL;DR

This paper demonstrates enhanced deep sub-Doppler cooling of $^{39}$K atoms using quantum interference in gray molasses, achieving temperatures around 12 μK and revealing the role of dark states and coherent effects.

Contribution

It introduces a novel cooling scheme leveraging quantum interference in a three-level system, achieving lower temperatures in $^{39}$K atoms with robust dark state formation.

Findings

Achieved cooling temperature of about 12 μK in $^{39}$K atoms.

Identified the role of dark states and quantum interference in cooling efficiency.

Showed that cooling occurs only for a small velocity class, requiring pre-cooling.

Abstract

We report enhanced sub-Doppler cooling of the bosonic atoms of $^{39}$K facilitated by formation of dark states tuned for the Raman resonance in the $\Lambda-$configuration near the D1 transition. Temperature of about 12 $\mu$K is achieved in the two stage D2-D1 molasses and spans a very large parameter region where quantum interference persists robustly. We also present results on enhanced radiation heating with sub-natural linewidth (0.07$\Gamma$) and signature Fano like profile of a coherently driven 3-level atomic system. The Optical Bloch Equations relevant for the three-level atom in bichromatic light field is solved with the method of continued fractions to show that cooling occurs only for a small velocity class of atoms, emphasizing the need for pre-cooling in D2 molasses stage.