Production of cold molecules via magnetically tunable Feshbach resonances

TL;DR

This paper reviews the use of magnetically tunable Feshbach resonances to produce and study cold diatomic molecules in Bose and Fermi gases, combining theoretical models with experimental techniques.

Contribution

It provides a comprehensive overview of the theoretical framework and experimental methods for creating and analyzing Feshbach molecules in cold gases.

Findings

Successful association of cold molecules via magnetic field tuning

Characterization of binding energies and lifetimes of Feshbach molecules

Analysis of molecular dynamics using Landau-Zener and mean field models

Abstract

Magnetically tunable Feshbach resonances were employed to associate cold diatomic molecules in a series of experiments involving both atomic Bose as well as two spin component Fermi gases. This review illustrates theoretical concepts of both the particular nature of the highly excited Feshbach molecules produced and the techniques for their association from unbound atom pairs. Coupled channels theory provides the rigorous formulation of the microscopic physics of Feshbach resonances in cold gases. Concepts of dressed versus bare energy states, universal properties of Feshbach molecules, as well as the classification in terms of entrance- and closed-channel dominated resonances are introduced on the basis of practical two-channel approaches. Their significance is illustrated for several experimental observations, such as binding energies and lifetimes with respect to collisional relaxation. Molecular association and dissociation are discussed in the context of techniques involving linear magnetic field sweeps in cold Bose and Fermi gases as well as pulse sequences leading to Ramsey-type interference fringes. Their descriptions in terms of Landau-Zener, two-level mean field as well as beyond mean field approaches are reviewed in detail, including the associated ranges of validity.