Bound states of two bosons in an optical lattice near an association resonance

TL;DR

This paper models two bosons in a one-dimensional optical lattice near a resonance, revealing the existence of two bound states in an atom-molecule framework, unlike the single state predicted by atoms-only models.

Contribution

It introduces an atom-molecule theory for bosons in an optical lattice near a resonance, predicting two bound states and expanding understanding of molecular physics in such systems.

Findings

Two bound states can occur simultaneously in an atom-molecule model.

Unusual molecular physics is observable with narrow Feshbach resonances or low-intensity photoassociation.

The model applies to specific atomic species like Na, Rb, Cs, and Yb.

Abstract

We model two bosons in an optical lattice near a Feshbach or photoassociation resonance, focusing on the Bose-Hubbard model in one dimension. Whereas the usual atoms-only theory with a tunable scattering length yields one bound state for a molecular dimer for either attractive or repulsive atom-atom interaction, an atom-molecule theory gives two bound states that may represent attractively and repulsively bound dimers occurring simultaneously. Such unusual molecular physics should be observable for an atom-molecule coupling strength comparable to the width of the dissociation continuum of the lattice dimer, for example, using narrow Feshbach resonances in Na, $^{87}$Rb, and $^{133}$Cs or low-intensity photoassociation in $^{174}$Yb.