Narrow-line magneto-optical cooling and trapping of strongly magnetic atoms

TL;DR

This paper demonstrates a novel narrow-line magneto-optical trap for strongly magnetic atoms like erbium, achieving ultracold, spin-polarized temperatures below 2 microkelvin by balancing optical and magnetic forces with blue-detuned laser light.

Contribution

It introduces an unconventional narrow-line MOT method for strongly magnetic atoms, overcoming destabilization issues present in conventional setups.

Findings

Achieved spin-polarized ultracold temperatures below 2 microkelvin.

Developed a stable MOT by tuning laser light to the blue side of a narrow transition.

Applicable to rare-earth and metastable alkaline earth elements.

Abstract

Laser cooling on weak transitions is a useful technique for reaching ultracold temperatures in atoms with multiple valence electrons. However, for strongly magnetic atoms a conventional narrow-line magneto-optical trap (MOT) is destabilized by competition between optical and magnetic forces. We overcome this difficulty in Er by developing an unusual narrow-line MOT that balances optical and magnetic forces using laser light tuned to the blue side of a narrow (8 kHz) transition. The trap population is spin-polarized with temperatures reaching below 2 microkelvin. Our results constitute an alternative method for laser cooling on weak transitions, applicable to rare-earth-metal and metastable alkaline earth elements.