Broad universal Feshbach resonances in the chaotic spectrum of Dysprosium atoms

TL;DR

This paper reports the discovery of broad, universal Feshbach resonances in Dysprosium atoms, revealing weakly-bound dimers with high magnetic moments that are decoupled from the chaotic resonance background, enabling tunable interactions.

Contribution

It demonstrates the existence of broad Feshbach resonances in Dysprosium and provides a coupled-channel theoretical analysis to characterize these resonances and their impact on interaction tunability.

Findings

Observation of weakly-bound Dysprosium dimers with high magnetic moments.

Identification of broad Feshbach resonances decoupled from narrow resonance background.

Measurement of scattering length and demonstration of interaction tunability.

Abstract

We report on the observation of weakly-bound dimers of bosonic Dysprosium with a strong universal s-wave halo character, associated with broad magnetic Feshbach resonances. These states surprisingly decouple from the chaotic backgound of narrow resonances, persisting across many such narrow resonances. In addition they show the highest reported magnetic moment $\mu\simeq20\,\mu_{\rm B}$ of any ultracold molecule. We analyze our findings using a coupled-channel theory taking into account the short range van der Waals interaction and a correction due to the strong dipole moment of Dysprosium. We are able to extract the scattering length as a function of magnetic field associated with these resonances and obtain a background scattering length $a_{\rm bg}=91(16)\,a_0$. These results offer prospects of a tunability of the interactions in Dysprosium, which we illustrate by observing the saturation of three-body losses.