无纠缠的非线性量子多自旋动力学

中文摘要 AI 辅助

我们引入了一种不同的途径，基于包含纯态和混合局域态的变分乘积态拟设，将经典原子自旋动力学扩展到任意自旋$s$的量子领域。通过构造，排除了位点间纠缠——在许多真实材料中，即使在极短时间尺度上，这种纠缠预计也可忽略——同时通过$s\geq 1$密度算符的非经典结构保留局域量子效应，非线性动力学源于局域态的均场相互依赖和依赖于态的耗散项。该框架阐明了量子Landau-Lifshitz与Landau-Lifshitz-Gilbert动力学不等价的变分和几何起源，提供了它们在共同时间重标度下等价的标准，通过两个定性不同的极限（$s\to\infty$和大量量子自旋$N$）与经典理论建立联系，并允许在材料中进行现实的$\mathcal{O}(N)$量子自旋动力学模拟。

英文摘要

We introduce a distinct route for extending classical atomistic spin dynamics into the quantum regime for arbitrary spin $s$, based on a variational product-state \textit{ansatz} that includes both pure and mixed local states. By construction, intersite entanglement -- expected to remain negligible even on very short time scales in many real materials -- is excluded, while local quantum effects are retained through the nonclassical structure of $s\geq 1$ density operators, and nonlinear dynamics arise from both the mean-field interdependence of the local states and the state-dependent dissipative terms. This framework clarifies the variational and geometric origin of the inequivalence between quantum Landau-Lifshitz and Landau-Lifshitz-Gilbert dynamics, provides a criterion for their equivalence under a common time rescaling, establishes connections with the classical theory through two qualitatively distinct limits ($s\to\infty$ and a large number of quantum spins $N$), and allows realistic $\mathcal{O}(N)$ simulations of quantum spin dynamics in materials.

发表机构

• Linnaeus University（林奈大学）
• Uppsala University（乌普萨拉大学）

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