由截断记忆效应产生的虚假自旋章动模式

中文摘要 AI 辅助

自旋动力学通常被视为无惯性的。惯性Landau-Lifshitz-Gilbert方程（iLLG）通过加入二阶时间导数扩展了这一描述，预测了一种高频章动模式，最近的实验声称观察到了该模式，并将其解释为自旋惯性的直接证据。我们证明，当通过消除额外的动力学自由度来产生自旋惯性时，所得出的精确纯自旋描述通常是非马尔可夫的。iLLG是在低频下对底层记忆核进行二阶截断而恢复的。利用一个最小自旋-腔模型，我们展示了精确的本征频率与通过iLLG获得的本征频率存在差异，且后者预测的自旋章动模式是一种由截断引起的高频伪影。这引发了一个更广泛的问题，即通过类似低频截断获得的iLLG的适用性，这种截断同样可能产生虚假的高频根。因此，高频光谱特征与iLLG章动频率的一致性本身并不能确立一个物理上的章动模式。

英文摘要

Spin dynamics is conventionally treated as inertia-free. The inertial Landau-Lifshitz-Gilbert equation (iLLG) extends this with a second-order time derivative, predicting a high-frequency nutational mode that recent experiments have claimed to observe and interpreted as direct evidence for spin inertia. We show that when spin inertia is generated by eliminating additional dynamical degrees of freedom, the resulting exact spin-only description is generally non-Markovian. The iLLG is recovered as the low-frequency, second-order truncation of the underlying memory kernel. Using a minimal spin--cavity model, we show that the exact eigenfrequencies and those obtained via the iLLG differ and that the spin nutation mode predicted by the latter is a truncation-induced high-frequency artifact. This raises a broader question of the applicability of the iLLG obtained from analogous low-frequency truncations, which may likewise generate spurious high-frequency roots. Consequently, agreement of a high-frequency spectral feature with the iLLG nutation frequency does not, by itself, establish a physical nutation mode.

发表机构

• Uppsala University（乌普萨拉大学）
• Indian Institute of Technology (ISM) Dhanbad（印度理工学院（ISM）丹巴德）

机构由 AI 辅助整理，请以论文原文为准。