标题： 量子微磁学理论中的有限纳米结构中的磁振子 显示英文标题

标题： Quantum Micromagnetic Theory of Magnons in Finite Nanostructures

摘要： 本文提出了一种量子场论形式化方法，用于研究具有任意形状和空间非均匀基态的有限纳米结构中的磁振子。 它通过引入一个包含交换、Dzyaloshinsky-Moriya、各向异性、磁静力和Zeeman能量的微观磁学哈密顿量量子算符，扩展了经典的微观磁学形式化方法。 通过逐点将磁化强度算符的量子化轴与经典基态对齐来处理基态的非均匀性。 在大自旋数极限下展开哈密顿量，并截断以仅保留与量子化轴垂直的磁化强度算符分量的二次项。 该二次哈密顿量用于推导线性量子Landau-Lifshitz方程。 通过在适当的边界和归一化条件下对这个方程进行对角化，得到一组离散的磁振子产生和湮灭算符，从而能够完整描述磁振子谱。 最后，该理论被应用于研究温度和形状对薄铁磁纳米盘中磁振子低温热平衡涨落的影响。 显示英文摘要

摘要： This paper presents a quantum field theoretical formalism for studying magnons in finite nanostructures with arbitrary shapes and spatially nonuniform ground states. It extends the classical micromagnetic formalism by introducing a micromagnetic Hamiltonian quantum operator, which incorporates exchange, Dzyaloshinsky-Moriya, anisotropy, magnetostatic, and Zeeman energies. The nonuniformity of the ground state is handled by pointwise aligning the quantization axis of the magnetization field operator with the classical ground state. The Hamiltonian is expanded in the large spin-number limit and truncated to retain only terms quadratic in the components of the magnetization operator transverse to the quantization axis. This quadratic Hamiltonian is used to derive the linear quantum Landau-Lifshitz equation. By diagonalizing this equation under appropriate boundary and normalization conditions, a discrete set of magnon creation and annihilation operators is obtained, enabling a complete description of the magnon spectrum. Finally, the theory is applied to study the effects of temperature and shape on low-temperature thermal equilibrium fluctuations of magnons in thin ferromagnetic nanodisks.