Magnetic trapping of ultracold molecules at high density

TL;DR

This paper demonstrates high-density magnetic trapping of ultracold NaLi molecules at microkelvin temperatures, enabling collision studies and sympathetic cooling without trapping light, advancing quantum simulation and chemistry applications.

Contribution

It reports the first magnetic trapping of NaLi molecules at high density and ultralow temperature, and shows sympathetic cooling increasing phase-space density significantly.

Findings

Achieved magnetic trapping of NaLi at ~10^11 cm^-3 density and 1 μK temperature.

Measured inelastic loss rates in various NaLi spin configurations.

Demonstrated sympathetic cooling of molecules via RF evaporation of co-trapped Na atoms.

Abstract

Trapping ultracold molecules in conservative traps is essential for applications -- such as quantum state-controlled chemistry, quantum simulations, and quantum information processing. These applications require high densities or phase-space densities. We report magnetic trapping of NaLi molecules in the triplet ground state at high density ($\approx 10^{11} \; \rm{cm}^{-3}$) and ultralow temperature ($\approx 1\;{\rm \mu K}$). Magnetic trapping at these densities allows studies on both atom-molecule and molecule-molecule collisions in the ultracold regime in the absence of trapping light, which has often lead to undesired photo-chemistry. We measure the inelastic loss rates in a single spin sample and spin-mixtures of fermionic NaLi as well as spin-stretched NaLi$+$Na mixtures. We demonstrate sympathetic cooling of NaLi molecules in the magnetic trap by radio frequency evaporation of co-trapped Na atoms and observe an increase in the molecules' phase-space density by a factor of $\approx 16$.