Creating a Quantum Degenerate Gas of Stable Molecules via Weak Photoassociation

TL;DR

This paper models a feasible method to produce quantum degenerate stable molecules from Bose-condensed atoms using low-intensity two-photon photoassociation, offering an alternative to magnetoassociation.

Contribution

It demonstrates a realistic, low-intensity laser approach for converting atomic condensates into molecular condensates via two-photon photoassociation.

Findings

Adiabatic laser frequency change converts atoms to molecules.

Feasible laser intensity for alkali-metal atoms is around 30 W/cm^2.

Method surpasses current magnetoassociation limitations.

Abstract

Quantum degenerate molecules represent a new paradigm for fundamental studies and practical applications. Association of already quantum degenerate atoms into molecules provides a crucial shortcut around the difficulty of cooling molecules to ultracold temperatures. Whereas association can be induced with either laser or magnetic fields, photoassociation requires impractical laser intensity to overcome poor overlap between the atom pair and molecular wavefunctions, and experiments are currently restricted to magnetoassociation. Here we model realistic production of a quantum degenerate gas of stable molecules via two-photon photoassociation of Bose-condensed atoms. An adiabatic change of the laser frequency converts the initial atomic condensate almost entirely into stable molecular condensate, even for low-intensity lasers. Results for dipolar LiNa provide an upper bound on the necessary photoassociation laser intensity for alkali-metal atoms ~30 W/cm^2, indicating a feasible path to quantum degenerate molecules beyond magnetoassociation.