基于最速熵上升量子热力学形式主义的磁铁矿中场驱动耦合磁振子-声子-电子弛豫

中文摘要 AI 辅助

本文开发了一种场驱动的最速熵上升量子热力学（SEAQT）形式主义，用于研究磁铁矿（Fe$_3$O$_4$）中电子、声子和磁振子耦合布居的纵向非平衡弛豫过程。材料特定的激发谱定义了热力学状态空间，每种布居对应一个弛豫参数以设定其动力学尺度。纵向磁场会改变修饰磁振子的本征能量，而占据基保持固定；不可逆的重新分布过程守恒瞬时能量和电子数，同时允许磁振子布居发生变化。该形式主义可得到非平衡子系统温度、熵产生、磁功恒等式，以及整合了三种布居间能量守恒反馈的耦合小信号 susceptibility；单极德拜响应仅作为极限情况出现。正弦驱动下的数值结果显示，系统会从近准静态行为转变为频率依赖的滞后，有限振幅偏离线性响应椭圆，且高次谐波含量增加。每周期的弛豫功随磁场振幅和频率显著增大，复 susceptibility 相对于德拜参考更宽且发生偏移；熵产生始终为正，当保留正磁功且无热量排出时，电子、声子和磁振子温度会出现不同的偏移，随后发生长期加热。计算得到的功代表均匀单畴模型中的纵向磁振子准粒子弛豫，而非有限铁氧体样品的总核心损耗。

英文摘要

A field-driven steepest-entropy-ascent quantum thermodynamic (SEAQT) formulation is developed for longitudinal nonequilibrium relaxation in magnetite (Fe$_3$O$_4$) with coupled electron, phonon, and magnon populations. Material-specific excitation spectra define the thermodynamic state space, while one relaxation parameter for each population sets its kinetic scale. A longitudinal magnetic field shifts the dressed magnon eigenenergies while the occupation basis remains fixed; irreversible redistribution conserves instantaneous energy and electron number while allowing the magnon population to vary. The formulation yields nonequilibrium subsystem temperatures, entropy production, magnetic-work identities, and a coupled small-signal susceptibility incorporating energy-conservation feedback among all three populations; the one-pole Debye response appears only as a limiting case. Numerical results under sinusoidal driving show a transition from nearly quasistatic behavior to frequency-dependent lag, finite-amplitude departure from the linear-response ellipse, and increasing higher-harmonic content. Relaxational work per cycle increases strongly with field amplitude and frequency, while the complex susceptibility is broader and shifted relative to a Debye reference. Entropy production remains positive, and the electron, phonon, and magnon temperatures show distinct excursions followed by secular heating when positive magnetic work is retained without heat rejection. The calculated work represents longitudinal magnon quasiparticle relaxation in a homogeneous single-domain model, not the total core loss of a finite ferrite specimen.

发表机构

• Virginia Tech（弗吉尼亚理工大学）

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