Chaotic scattering in the presence of a dense set of overlapping Feshbach resonances

TL;DR

This paper investigates how overlapping Feshbach resonances influence the distribution of resonance spacings in complex quantum systems, revealing a spectrum that transitions from non-Poisson to semi-Poisson behavior.

Contribution

It demonstrates that strongly overlapping Feshbach resonances produce a non-Poisson spectrum that is not fully chaotic, extending understanding beyond traditional Random Matrix Theory predictions.

Findings

Resonance spectrum becomes non-Poisson with overlap

Spectrum tends towards semi-Poisson distribution

Overlapping resonances affect level spacing statistics

Abstract

Complex quantum systems consisting of large numbers of strongly coupled states exhibit characteristic level repulsion, leading to a non-Poisson spacing distribution which can be described by Random Matrix Theory. Scattering resonances observed in ultracold atomic and molecular systems exhibit similar features as a consequence of their energy level structure. We study how the overlap between Feshbach resonances affects the distribution of resonance spacings. The spectrum of strongly overlapping resonances turns out to be non-Poisson even when the assumptions of Random Matrix Theory are not fulfilled, but the spectrum is also not completely chaotic and tends towards being semi-Poisson.