Multichannel Quantum Defect Theory with a Frame Transformation for Ultracold Atom-Molecule Collisions in Magnetic Fields

Recent advances in cooling and trapping diatomic and polyatomic molecules have established ultracold molecular gases as an emerging platform for quantum information science, ultracold chemistry, and precision searches for new physics beyond the standard model. The exquisite control over molecular degrees of freedom achieved in these experiments enables the exploration of novel regimes of ultracold chemical dynamics tunable by external electromagnetic fields.

Publication Date: 26 August, 2024

Authors: Masato Morita, Paul Brumer, and Timur V. Tscherbul

Abstract:

We extend the powerful formalism of multichannel quantum defect theory combined with a frame transformation to ultracold atom-molecule collisions in magnetic fields. By solving the coupled-channel equations with hyperfine and Zeeman interactions omitted at short range, the extended theory enables a drastically simplified description of the intricate quantum dynamics of ultracold molecular collisions in terms of a small number of short-range parameters. We apply the formalism to ultracold Mg+NH collisions in a magnetic field, achieving a 104-fold reduction in computational effort.

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