Magnetic systems can be described by the classical Landau-Lifshitz (LL) equation or the fully quantum open Heisenberg model. Using the Lindblad master equation and the mean-field approximation, we demonstrate that the open Heisenberg model is reduced to a generalized LL equation. The open dynamic is modeled using spin-boson interactions with a common bosonic reservoir at thermal equilibrium. By tracing out the bosonic degrees of freedom, we obtain two different decoherence mechanisms: on-site dissipation and an effective spin-spin interaction mediated by bosons. Using our approach, we perform hysteresis calculations, closely connected with the Stoner-Wohlfarth theory. We compare the exact numerical master equation and the mean-field model, revealing the role of correlations originated by non-local interactions. Our work opens new horizons for the study of the LL dynamics from an open quantum formalism.

中文翻译：

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从开放海森堡模型到 Landau-Lifshitz 方程

磁系统可以用经典的 Landau-Lifshitz (LL) 方程或完全量子开放的海森堡模型来描述。使用 Lindblad 主方程和平均场近似，我们证明开放海森堡模型被简化为广义 LL 方程。开放动力学使用自旋玻色子相互作用与热平衡下的普通玻色子储层进行建模。通过追踪玻色子自由度，我们获得了两种不同的退相干机制：现场耗散和由玻色子介导的有效自旋-自旋相互作用。使用我们的方法，我们执行滞后计算，与 Stoner-Wohlfarth 理论密切相关。我们比较了精确的数值主方程和平均场模型，揭示了非局部相互作用产生的相关性的作用。