Unconventional quantum spin mixing of two spin-1 atoms beyond the single-mode approximation
Abstract
The single-mode approximation (SMA) has been widely employed in ultracold spinor gases, where all spin components share the same spatial mode. By adopting generalized Van Vleck (GVV) perturbation theory, we achieve a relative error of 10−6 in the ground-state energy with a reduced effective Hilbert space dimension of ∼ 103 for two spin-1 bosons confined in a one-dimensional hard-wall trap. With the accurate GVV method, we explore the validity of the SMA across ground-state properties and quench spin dynamics for two 7Li, 87Rb, or 23Na atoms. Numerical results show that the quadratic Zeeman energy q provides a powerful control knob: by increasing |q|, the fidelity between the spin components in the ground state gradually decreases, leading eventually to the breakdown of the SMA (due to the competition between the kinetic energy and the quadratic Zeeman energy). Quench spin dynamics with abruptly increased q further reveals multiple resonances, where the SMA-predicted micromotion and beyond-SMA macromotion appear simultaneously. These results point to a direction to investigate the quantum spin-mixing dynamics beyond the SMA, particularly in recent experiments of strongly interacting spin-1 atomic gases.
Versions
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BibTeX
@misc{liu2026unconventional,
title = {{Unconventional quantum spin mixing of two spin-1 atoms beyond the single-mode approximation}},
author = {Yanhong Liu and Fulin Deng and Haoxue Qiao and Wenxian Zhang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.20096},
eprint = {2610.20096},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.20096},
}
RIS
TY - UNPB
TI - Unconventional quantum spin mixing of two spin-1 atoms beyond the single-mode approximation
AU - Yanhong Liu
AU - Fulin Deng
AU - Haoxue Qiao
AU - Wenxian Zhang
PY - 2026
DA - 2026/10/14
PB - arXiv
DO - 10.48550/arxiv.2610.20096
UR - https://arxiv.org/abs/2610.20096
AB - The single-mode approximation (SMA) has been widely employed in ultracold spinor gases, where all spin components share the same spatial mode. By adopting generalized Van Vleck (GVV) perturbation theory, we achieve a relative error of 10^−6 in the ground-state energy with a reduced effective Hilbert space dimension of ∼ 10^3 for two spin-1 bosons confined in a one-dimensional hard-wall trap. With the accurate GVV method, we explore the validity of the SMA across ground-state properties and quench spin dynamics for two ^7Li, ^87Rb, or ^23Na atoms. Numerical results show that the quadratic Zeeman energy q provides a powerful control knob: by increasing |q|, the fidelity between the spin components in the ground state gradually decreases, leading eventually to the breakdown of the SMA (due to the competition between the kinetic energy and the quadratic Zeeman energy). Quench spin dynamics with abruptly increased q further reveals multiple resonances, where the SMA-predicted micromotion and beyond-SMA macromotion appear simultaneously. These results point to a direction to investigate the quantum spin-mixing dynamics beyond the SMA, particularly in recent experiments of strongly interacting spin-1 atomic gases.
ER -