arXiv:2401.18003 · New Journal of Physics

Chaotic scattering in ultracold atom-ion collisions

Meirav Pinkas, Jonathan M. Wengrowicz, Nitzan Akerman, Roee Ozeri

Published Sep 4, 2026• 1 citation

Abstract

Abstract we report on signatures of classical chaos in ultracold collisions between a trapped ion and a free atom. Using numerical simulations, we show that the scattering dynamics can be highly sensitive to initial conditions for various mass ratios and trapping frequencies, indicating the onset of chaos. We quantify this chaotic dynamics by calculating its fractal dimension. We show that for a trapped 88 Sr + ion and a free 87 Rb atom chaotic dynamic appears under experimentally relevant conditions, and find its characteristic energy scale. The observation of classical chaos in atom-trapped-ion collisions suggests that signatures of quantum chaos might appear, for example, through a Wigner–Dyson distribution of collisional resonances.

DOI: 10.1088/1367-2630/aea2bc

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arXiv:2401.18003 · New Journal of Physics

Chaotic scattering in ultracold atom-ion collisions

Meirav Pinkas, Jonathan M. Wengrowicz, Nitzan Akerman, Roee Ozeri

Published Sep 4, 2026• 1 citation

arXiv HTML PDF

Abstract

DOI: 10.1088/1367-2630/aea2bc

Related papers

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arXiv:1510.06992Physical Review AFeb 4, 201617 citations

We study the classical dynamics of a Paul-trapped ion in a low-density bath of atoms above 1

μ\textrm{K}

. We find that lower energy collisions with more massive atoms, especially at energies less than the initial micromotion heating, are more likely to form atom-ion complexes. These complexes evolve in a fractal structure for every scattering observable, showing non-hyperbolic chaotic dynamics. To explore the chaotic dynamics, we use a GPU-accelerated methodology allowing us to run over

3\times 10^{8}

trajectories of a

^{174}

^+

and different atoms. As a result, after analyzing the dynamics as a function of the atom species, collision energy, trap parameters, and ion-atom potential depth, we find a link between heating and the onset of chaos in the first atom-ion interaction that occurs when a low-density atomic bath is merged with a trapped ion.

{\mathrm{K}}_{2}

with Rb are reported, from numerically exact quantum-scattering calculations. Thermally averaged lifetimes are compared with those calculated using a simple density-of-states approach, which are shown to be reasonable. This validates the density-of-states approach and suggests that the formation of long-lived complexes is indeed the cause of observed experimental trap loss in ultracold alkali-metal-dimer systems. Long-lived complexes correspond to narrow scattering resonances which we examine for the statistical signatures of quantum chaos, finding that the positions and widths of the resonances are in good agreement with the Wigner-Dyson and Porter-Thomas distributions, respectively.

We present a fully quantum mechanical description of a free

^{6}\mathrm{Li}

atom scattering from a trapped

^{171}\mathrm{Yb}^{+}

ion in one dimension. By reformulating the system in polar coordinates and employing the adiabatic representation, we extract a set of coupled adiabatic potentials representing the atom interacting with the ion in different trap states. In an approach similar to quantum defect theory, we leverage the vast difference in energy scale between the interaction, the trap, and the scattering energy to encapsulate the short-range atom-ion scattering behavior in a single phase parameter. The presence of trapped

{(^{171}\mathrm{Yb}^{6}\mathrm{Li})}^{+}

molecular-ion states leads to a series of roughly evenly spaced resonances in the scattering cross section. The predicted distribution of resonances at low collision energies is at odds with the expectation of quantum chaos and the Bohigas-Giannoni-Schmit conjecture.

We calculate and analyze Feshbach resonance spectra for ultracold

\mathrm{Yb}({}^{1}{S}_{0})+\mathrm{Yb}({}^{3}{P}_{2})

collisions as a function of an interatomic potential scaling factor $\ensuremath{\lambda}$ and external magnetic field. We show that, at zero field, the resonances are distributed randomly in $\ensuremath{\lambda}$, but that signatures of quantum chaos emerge as a field is applied. The random zero-field distribution arises from superposition of structured spectra associated with individual total angular momenta. In addition, we show that the resonances with respect to magnetic field in the experimentally accessible range of 400 to 2000 G are chaotically distributed, with strong level repulsion that is characteristic of quantum chaos.