Multichannel effects in the Efimov regime from broad to narrow Feshbach resonances

TL;DR

This paper investigates how multichannel interactions influence Efimov states in three-boson systems near Feshbach resonances of varying widths, revealing the role of closed-channel trimer states and resonance width in shaping the universal spectrum.

Contribution

It demonstrates that the two-body multichannel nature affects the Efimov spectrum, especially at intermediate resonance widths, and clarifies the spectrum's dependence on resonance width in narrow and broad limits.

Findings

Multichannel effects modify the Efimov spectrum at intermediate widths.

In the narrow resonance limit, the spectrum depends solely on the width parameter $r^*$.

In the broad resonance limit, Efimov energies match single-channel predictions.

Abstract

We study Efimov physics of three identical bosons with pairwise multichannel interactions for Feshbach resonances of adjustable width. We find that the two-body multichannel nature of the interaction can affect the universal three-body spectrum, especially for resonances of intermediate width. The shifts in this universal spectrum are caused by trimer states in the closed interaction channels that couple to the universal Efimov states. However, in the narrow resonance limit we find that the Efimov spectrum is set by the resonance width parameter $r^*$ only independent of the interaction potential considered. In the broad resonance limit all excited Efimov trimer energies approach the ones from the corresponding single-channel system for the scenarios investigated.