Formation and Dissociation of Field-Linked Tetramers

TL;DR

This paper explores the formation, stability, and detection of field-linked tetramers of microwave-shielded polar molecules, revealing longer lifetimes for higher states and multi-photon dissociation processes, with implications for quantum gas cooling.

Contribution

It provides new insights into the properties, detection methods, and dissociation mechanisms of field-linked tetramers, extending understanding to universal inter-molecular potentials.

Findings

Higher tetramer states have longer lifetimes.

Distinctive time-of-flight images can detect tetramers.

Multi-photon processes induce dissociation below threshold.

Abstract

We investigate the static and dynamic properties of tetratomic molecules formed by two microwave-shielded polar molecules across field-linked resonances. In particular, we focus on two-body physics and experimental techniques unexplored in the recent experiment [X.-Y. Chen {\it et al}., Nature {\bf626}, 283 (2024)]. We show that, compared to the lowest tetramer state, higher tetramer states typically have longer lifetimes, which may facilitate a further cooling of tetramer gases towards quantum degeneracy. To detect tetramers, we identify the distinctive time-of-flight images from ramp dissociation, which can be observed by lowering the ramp rate of the microwave. Remarkably, in the modulational dissociation of tetramers, we find that multi-photon processes induce dissociation even below the threshold modulation frequency when the modulation amplitude is sufficiently high. Given the universal form of the inter-molecular potential for microwave-shielded polar molecules, our results also apply to other molecular gases widely explored in recent experiments.