Towards improved loading, cooling, and trapping of molecules in magneto-optical traps

TL;DR

This paper discusses recent advances and challenges in cooling and trapping molecules in magneto-optical traps, proposing simulation-based solutions to improve density and loading efficiency for quantum degeneracy.

Contribution

The paper introduces simulation methods to overcome key limitations in molecular MOTs caused by Type-II transitions and sub-Doppler heating, aiming to enhance trap density and loading.

Findings

Simulations identify strategies to mitigate slowing inefficiencies.

Proposed methods improve MOT capture velocities.

Potential to load molecules into high-density traps for quantum degeneracy.

Abstract

Recent experiments have demonstrated direct cooling and trapping of diatomic and triatomic molecules in magneto-optical traps (MOTs). However, even the best molecular MOTs to date still have density $10^{-5}$ times smaller than in typical atomic MOTs. The main limiting factors are: (i) inefficiencies in slowing molecules to velocities low enough to be captured by the MOT, (ii) low MOT capture velocities, and (iii) limits on density within the MOT resulting from sub-Doppler heating~[J. A. Devlin and M. R. Tarbutt, Phys. Rev. A \textbf{90}, 063415 (2018)]. All of these are consequences of the need to drive `Type-II' optical cycling transitions, where dark states appear in Zeeman sublevels, in order to avoid rotational branching. We present simulations demonstrating ways to mitigate each of these limitations. This should pave the way towards loading molecules into conservative traps with sufficiently high density and number to evaporatively cool them to quantum degeneracy.