Preparation and spectroscopy of a metastable Mott insulator state with attractive interactions

TL;DR

This study demonstrates the creation of a metastable attractive Mott insulator state with bosonic atoms in an optical lattice, revealing interaction-dependent spectra and loss mechanisms.

Contribution

It introduces a method to prepare and analyze a metastable attractive Mott insulator state using Feshbach resonance tuning.

Findings

Metastable state lifetime of about 10 seconds.

Observation of interaction-dependent two- and three-body bound states.

Resonance broadening and suppression of tunneling due to three-body loss.

Abstract

We prepare and study a metastable attractive Mott insulator state formed with bosonic atoms in a three-dimensional optical lattice. Starting from a Mott insulator with Cs atoms at weak repulsive interactions, we use a magnetic Feshbach resonance to tune the interactions to large attractive values and produce a metastable state pinned by attractive interactions with a lifetime on the order of 10 seconds. We probe the (de-)excitation spectrum via lattice modulation spectroscopy, measuring the interaction dependence of two- and three-body bound state energies. As a result of increased on-site three-body loss we observe resonance broadening and suppression of tunneling processes that produce three-body occupation.