Mott-Insulator-Aided Detection of Ultra-Narrow Feshbach Resonances

TL;DR

This paper demonstrates a method using a Mott-insulating state in an optical lattice to detect ultra-narrow Feshbach resonances in cesium atoms, revealing new resonances and substructures with high precision.

Contribution

The study introduces a novel technique employing a Mott insulator to detect and characterize ultra-narrow Feshbach resonances, surpassing limitations of bulk sample measurements.

Findings

Detected three ultra-narrow Feshbach resonances below 10 μG width

Observed lattice-induced substructure in atom-loss features

Confirmed resonances with theoretical predictions

Abstract

We report on the detection of extremely narrow Feshbach resonances by employing a Mott-insulating state for cesium atoms in a three-dimensional optical lattice. The Mott insulator protects the atomic ensemble from high background three-body losses in a magnetic field region where a broad Efimov resonance otherwise dominates the atom loss in bulk samples. Our technique reveals three ultra-narrow and previously unobserved Feshbach resonances in this region with widths below $\approx 10\,\mu$G, measured via Landau-Zener-type molecule formation and confirmed by theoretical predictions. For comparatively broader resonances we find a lattice-induced substructure in the respective atom-loss feature due to the interplay of tunneling and strong particle interactions. Our results provide a powerful tool to identify and characterize narrow scattering resonances, particularly in systems with complex Feshbach spectra. The observed ultra-narrow Feshbach resonances could be interesting candidates for precision measurements.