Doublon dynamics and polar molecule production in an optical lattice

TL;DR

This paper investigates the dynamics of doublons and the production of polar molecules in an optical lattice, revealing interaction effects, tunneling regimes, and probing techniques for heteronuclear systems.

Contribution

It provides experimental insights into doublon dynamics, explores regimes of tunneling, and introduces methods to probe microscopic distributions in heteronuclear lattice systems.

Findings

Interaction effects influence pairing and doublon behavior.

Tunneling dynamics vary between fermions-only and mixed species regimes.

Inelastic doublon loss measurements reveal microscopic distributions.

Abstract

Ultracold polar molecules provide an excellent platform to study quantum many-body spin dynamics, which has become accessible in the recently realized low entropy quantum gas of polar molecules in an optical lattice. To obtain a detailed understanding for the molecular formation process in the lattice, we prepare a density distribution where lattice sites are either empty or occupied by a doublon composed of a bosonic atom interacting with a fermionic atom. By letting this disordered, out-of-equilibrium system evolve from a well-defined initial condition, we observe clear effects on pairing that arise from inter-species interactions, a higher partial wave Feshbach resonance, and excited Bloch-band population. When only the lighter fermions are allowed to tunnel in the three-dimensional (3D) lattice, the system dynamics can be well described by theory. However, in a regime where both fermions and bosons can tunnel, we encounter correlated dynamics that is beyond the current capability of numerical simulations. Furthermore, we show that we can probe the microscopic distribution of the atomic gases in the lattice by measuring the inelastic loss of doublons. These techniques realize tools that are generically applicable to heteronuclear diatomic systems in optical lattices and can shed light on molecule production as well as dynamics of a Bose-Fermi mixture.