Wider research context / theoretical framework

Interactions between particles are at the heart of fascinating quantum phenomena such as the Berezinskii-Kosterlitz-Thauless transition or the superfluid to Mott insulator transition, the emergence of composite objects such as solitons or vortices, or the creation of new bound states such as ultracold molecules or Effimov trimers.

These exciting phenomena become accessible for selected alkali atoms through Fano-Feshbach resonances (FFR), when a quasibound molecular state becomes resonant with a free state of the colliding atoms.

Hypotheses/research questions /objectives

Up to now, all experimental implementation of FFR have used quasi-static magnetic fields or optical fields and are limited to specific atomic isotopes. These approaches are burdened with the need to control high magnetic fields with great accuracy and/or reduced lifetimes due to photon scattering, respectively. Many commonly used alkali Atoms don’t provide FFRs at all.

Here we will investigate a new approach to tuning of atomic interactions using strong radiofrequency (RF) and microwave (MW) fields. A multitude of theoretical proposals have predicted RF/MW-induced FFRs, for a broad range of atomic species and states (including magnetically trappable ones) but they have not been explored experimentally yet.

Approach/methods

RF/MW-induced FFRs require very strong amplitudes of rapidly oscillating magnetic fields, hardly accessible in conventional cold atom experiments. Such fields can be generated using atom-chip near fields; however, these predominantly use magnetically trapped Rubidium atoms, where the resonances are predicted to narrow and accompanied with strong losses.

Here we will employ two atom-chip setups specifically built to explore RF/MW-induces FFRs using Cesium and Sodium, where FFRs are expected to be broad due to near-threshold molecular states. Our collaborative approach combines two atomic species, optical and magnetic trapping, as well as control over the systems dimensionality and internal degrees of freedom.

Level of originality / innovation

Demonstrating RF/MW-induced FFRs would add a game-changing component to the cold-atoms-toolbox. Interaction tuning would become accessible to a much broader range of atomic species and states, including magnetically trappable low-field seekers. In this proposal we will explore applications to atomic clocks, interferometry and low-dimensional many-body physics, but many more can be envisioned.

Primary researchers involved

The project involves two experimental teams from Vienna (PI Thorsten Schumm) and Paris (PI Aurélin Perrin) with extensive experience in the chip-based manipulations of ultracold alkali atoms, a well-established track record of collaborative work and two fully built experimental setups, specifically build and ready to explore RF/MW-induced FFRs.