Field-linked resonances of polar molecules

TL;DR

This paper introduces a universal new type of scattering resonance for ultracold polar molecules, called field-linked resonances, which allow precise control over molecular interactions using microwave fields, enabling advances in quantum many-body physics.

Contribution

The study demonstrates the existence of field-linked resonances in ultracold polar molecules and shows how microwave tuning can control inelastic collisions and interactions.

Findings

Resonances occur due to stable tetramer states in the intermolecular potential.

Microwave frequencies and polarizations can tune the inelastic collision rate by three orders of magnitude.

Control over elastic and dipole-dipole interactions was achieved, affecting thermalization rates.

Abstract

Scattering resonances are an essential tool for controlling interactions of ultracold atoms and molecules. However, conventional Feshbach scattering resonances, which have been extensively studied in various platforms, are not expected to exist in most ultracold polar molecules due to the fast loss that occurs when two molecules approach at a close distance. Here, we demonstrate a new type of scattering resonances that is universal for a wide range of polar molecules. The so-called field-linked resonances occur in the scattering of microwave-dressed molecules due to stable macroscopic tetramer states in the intermolecular potential. We identify two resonances between ultracold ground-state sodium-potassium molecules and use the microwave frequencies and polarizations to tune the inelastic collision rate by three orders of magnitude, from the unitary limit to well below the universal regime. The field-linked resonance provides a tuning knob to independently control the elastic contact interaction and the dipole-dipole interaction, which we observe as a modification in the thermalization rate. Our result provides a general strategy for resonant scattering between ultracold polar molecules, which paves the way for realizing dipolar superfluids and molecular supersolids as well as assembling ultracold polyatomic molecules.