Efimov resonances above four-boson threshold

TL;DR

This paper investigates Efimov resonances above the four-boson breakup threshold, revealing their evolution into resonances with universal properties and analyzing their impact on four-particle recombination rates.

Contribution

It provides a rigorous analysis of Efimov tetramers above the four-boson threshold, demonstrating their resonance behavior and universal scaling in this regime.

Findings

Efimov tetramers become resonances with finite widths above the threshold.

Resonance widths increase rapidly but remain narrower than associated trimers.

Four-particle recombination rates exhibit clear resonance signatures.

Abstract

Four-boson Efimov physics is well known in the negative energy regime but far less above the four-body breakup threshold. The part of this region with negative two-boson scattering length is studied solving rigorous four-particle scattering equations for transition operators in the momentum space. Moving away from the unitary limit the Efimov tetramers evolve from unstable bound states into resonances. Their energies and widths are studied as functions of the two-boson scattering length; a universal behavior is established and given in a dimensionless representation. The Efimov tetramers have finite width in the whole regime; they broaden rapidly in the resonance regime but remain narrower than the associated trimer. The resonant behavior is most clearly seen in the four-particle recombination rate.