Ultracold nonreactive molecules in an optical lattice: connecting chemistry to many-body physics

TL;DR

This paper develops effective lattice models for ultracold nonreactive molecules, revealing multi-channel interactions that differ from the traditional Hubbard model, and proposes experimental methods to measure molecular collision dynamics with high energy resolution.

Contribution

It introduces a multi-channel interaction framework for nonreactive molecules in optical lattices, extending beyond the single-parameter Hubbard model and linking collision physics to many-body phenomena.

Findings

Multi-channel interactions replace the single U parameter in lattice models.

A crossover from coherent to incoherent models is observed with increasing lattice depth.

Lattice modulation experiments can precisely measure molecular collision dynamics.

Abstract

We derive effective lattice models for ultracold bosonic or fermionic nonreactive molecules (NRMs) in an optical lattice, analogous to the Hubbard model that describes ultracold atoms in a lattice. In stark contrast to the Hubbard model, which is commonly assumed to accurately describe NRMs, we find that the single on-site interaction parameter $U$ is replaced by a multi-channel interaction, whose properties we elucidate. The complex, multi-channel collisional physics is unrelated to dipolar interactions, and so occurs even in the absence of an electric field or for homonuclear molecules. We find a crossover between coherent few-channel models and fully incoherent single-channel models as the lattice depth is increased. We show that the effective model parameters can be determined in lattice modulation experiments, which consequently measure molecular collision dynamics with a vastly sharper energy resolution than experiments in an ultracold gas.