Microscopy of an ultranarrow Feshbach resonance using a laser-based atom collider: A quantum defect theory analysis

Abstract

We employ a quantum defect theory framework to provide a detailed analysis of the interplay between a magnetic Feshbach resonance and a shape resonance in cold collisions of ultracold ${}^{87}\mathrm{Rb}$ atoms as captured in recent experiments using a laser-based collider [Phys. Rev. Research 3, 033209 (2021)]. By exerting control over a parameter space spanned by both collision energy and magnetic field, the width of a Feshbach resonance can be tuned over several orders of magnitude. We apply a quantum defect theory specialized for ultracold atomic collisions to fully describe of the experimental observations. While the width of a Feshbach resonance generally increases with collision energy, its coincidence with a shape resonance leads to a significant additional boost. By conducting experiments at a collision energy matching the shape resonance and using the shape resonance as a magnifying lens we demonstrate a feature broadening to a magnetic width of 8 G compared to a predicted Feshbach resonance width $\ll 0.1$~mG.

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Cited by in corpus (5)

• Observing S-Matrix Pole Flow in Resonance Interplay: Cold Collisions of Ultracold Atoms in a Miniature Laser-based Accelerator
• Closed-channel parameters of Feshbach resonances
• Resonance-facilitated three-channel p-wave scattering
• Scattering Angle Dependence of Fano Resonance Profiles in Cold Atomic Collisions Analyzed with the Complex Valued $w$ Parameter
• Universality and threshold laws for collision lifetimes at ultralow temperatures