Controlling the scattering length of ultracold dipolar molecules

TL;DR

This paper demonstrates how microwave fields can be used to tune the scattering length of ultracold dipolar molecules, enabling control over their interactions for advanced many-body physics applications.

Contribution

It introduces a method to control the scattering length of dipolar molecules using microwave fields, with a detailed adimensional approach and implications for suppressing quenching losses.

Findings

Molecular scattering length can be tuned from negative to positive values.

High rotational constant molecules are immune to quenching with sufficient microwave field.

Elastic to quenching process ratio can exceed 1000.

Abstract

By applying a circularly polarized and slightly blue-detuned microwave field with respect to the first excited rotational state of a dipolar molecule, one can engineer a long-range, shallow potential well in the entrance channel of the two colliding partners. As the applied microwave ac-field is increased, the long-range well becomes deeper and can support a certain numbers of bound states, which in turn bring the value of the molecule-molecule scattering length from a large negative value to a large positive one. We adopt an adimensional approach where the molecules are described by a rescaled rotational constant $\tilde{B} = B/s_{E_3} $ where $s_{E_3}$ is a characteristic dipolar energy. We found that molecules with $\tilde{B} > 10^8$ are immune to any quenching losses when a sufficient ac-field is applied, the ratio elastic to quenching processes can reach values above $10^3$, and that the value and sign of the scattering length can be tuned. The ability to control the molecular scattering length opens the door for a rich, strongly correlated, many-body physics for ultracold molecules, similar than that for ultracold atoms.