Observation of Fano-suppression in scattering resonances of bosonic erbium atoms

TL;DR

This study observes Fano-suppression in scattering resonances of bosonic erbium atoms, revealing complex multi-channel interference effects and opening avenues for exploring multi-spin strongly-coupled scattering phenomena.

Contribution

It demonstrates Fano interference effects in bosonic erbium scattering resonances and develops a simplified model to explain their asymmetric shapes and multi-channel interactions.

Findings

Detection of asymmetric Fano-like scattering resonances

Development of a multi-channel interference model

Observation of Fano-Feshbach resonances across spin channels

Abstract

The collisional properties of lanthanides exhibit remarkable complexity due to their many valence electrons, leading to an extraordinarily dense Feshbach spectrum showing signs of quantum chaos. Here we explore the situation of bosonic spin mixtures of erbium, adding the additional spin degree of freedom to the problem. We detect several inter- and intra-spin scattering resonances, exhibiting a peculiar asymmetric shape with a pronounced loss minimum. By developing a simplified multi-channel model we are able to recreate this characteristic behavior and to trace its origin to destructive interference between multiple pathways as predicted by Fano. We additionally observe a series of Fano-Feshbach resonances across multiple spin channels connected to the same molecular state, again confirmed by our theory. Our work opens the door for a detailed investigation to study multi-spin strongly-coupled scattering phenomena.