Reshaped Three-Body Interactions and the Observation of an Efimov State in the Continuum

TL;DR

This paper investigates the behavior of Efimov states near the atom-dimer threshold in $^7$Li atoms, revealing a universal metastable state due to reshaped three-body interactions caused by a narrow Feshbach resonance.

Contribution

It demonstrates that Efimov trimers can remain metastable in the continuum, challenging previous expectations and highlighting the role of a universal repulsive interaction in narrow Feshbach resonances.

Findings

Efimov state persists as a metastable state in the atom-dimer continuum.

Reshaped three-body interactions are universal across systems with narrow Feshbach resonances.

Provides insights into the nature of $^7$Li Efimov states and related phenomena.

Abstract

Efimov trimers are exotic three-body quantum states that emerge from the different types of three-body continua in the vicinity of two-atom Feshbach resonances. In particular, as the strength of the interaction is decreased to a critical point, an Efimov state merges into the atom-dimer threshold and eventually dissociates into an unbound atom-dimer pair. Here we explore the Efimov state in the vicinity of this critical point using coherent few-body spectroscopy in $^7$Li atoms using a narrow two-body Feshbach resonance. Contrary to the expectation, we find that the $^7$Li Efimov trimer does not immediately dissociate when passing the threshold, and survives as a metastable state embedded in the atom-dimer continuum. We identify this behavior with a universal phenomenon related to the emergence of a repulsive interaction in the atom-dimer channel which reshapes the three-body interactions in any system characterized by a narrow Feshbach resonance. Specifically, our results shed light on the nature of $^7$Li Efimov states and provide a path to understand various puzzling phenomena associated with them.