磁体的量子布朗运动
Quantum Brownian Motion for Magnets
摘要：
磁性材料中的自旋进动通常用经典的唯象Landau-Lifshitz-Gilbert（LLG）方程来模拟。基于量子化的自旋+环境哈密顿量，我们在这里推导出一个通用的自旋算符的运动运动方程，它描述了三维的进动和阻尼，并始终占所产生的记忆，色噪声和量子统计的影响。LLG方程恢复为经典的欧姆近似。我们进一步介绍共振洛伦兹系统-水库耦合，允许欧姆和非欧姆制度之间的动态系统的比较。最后，我们模拟了自旋在半经典极限下的完全非马尔可夫动力学。在低温下，我们的数值计算结果表明了一个特征的减少和平坦的稳定状态的自旋对齐与外场，所造成的量子统计环境。这些结果为探讨量子热力学中的一般三维耗散提供了一个强有力的框架。
英文摘要：
Spin precession in magnetic materials is commonly modelled with the classical phenomenological Landau-Lifshitz-Gilbert (LLG) equation. Based on a quantized spin+environment Hamiltonian, we here derive a general spin operator equation of motion that describes three-dimensional precession and damping and consistently accounts for effects arising from memory, coloured noise and quantum statistics. The LLG equation is recovered as its classical, Ohmic approximation. We further introduce resonant Lorentzian system--reservoir couplings that allow a systematic comparison of dynamics between Ohmic and non--Ohmic regimes. Finally, we simulate the full non-Markovian dynamics of a spin in the semi--classical limit. At low temperatures, our numerical results demonstrate a characteristic reduction and flattening of the steady state spin alignment with an external field, caused by the quantum statistics of the environment. The results provide a powerful framework to explore general three-dimensional dissipation in quantum thermodynamics.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
