Creation and manipulation of Feshbach resonances with radio-frequency radiation

TL;DR

This paper introduces a straightforward method to control ultracold atomic collisions using radio-frequency radiation and magnetic fields, enabling resonance tuning with minimal losses and potential applications in various atomic species.

Contribution

It demonstrates how rf radiation can be used to manipulate Feshbach resonances and scattering properties in ultracold atoms, including halo molecules, with detailed analysis of underlying physics.

Findings

Rf coupling can control scattering without losses in some conditions.

Halo molecules require less rf power than deeply bound states.

Rf and magnetic fields together offer versatile tuning mechanisms.

Abstract

We present a simple technique for studying collisions of ultracold atoms in the presence of a magnetic field and radio-frequency radiation (rf). Resonant control of scattering properties can be achieved by using rf to couple a colliding pair of atoms to a bound state. We show, using the example of 6Li, that in some ranges of rf frequency and magnetic field this can be done without giving rise to losses. We also show that halo molecules of large spatial extent require much less rf power than deeply bound states. Another way to exert resonant control is with a set of rf-coupled bound states, linked to the colliding pair through the molecular interactions that give rise to magnetically tunable Feshbach resonances. This was recently demonstrated for 87Rb [Kaufman et al., Phys. Rev. A 80:050701(R), 2009]. We examine the underlying atomic and molecular physics which made this possible. Lastly, we consider the control that may be exerted over atomic collisions by placing atoms in superpositions of Zeeman states, and suggest that it could be useful where small changes in scattering length are required. We suggest other species for which rf and magnetic field control could together provide a useful tuning mechanism.