All-optical helicity-dependent manipulations of magnetism have attracted broad attention in the context of ultrafast control of magnetic units. Here, we investigate the spin dynamics in time reversal symmetric insulators induced by strong circularly polarized light. We perform real-time time-dependent density functional theory calculations together with model Hamiltonian analyses for $\mathrm{Mo}{\mathrm{S}}_2$ and $\mathrm{W}{\mathrm{S}}_2$ monolayers, which are exemplary spin-orbit-coupled time reversal symmetric insulators. We trace the evolution of dynamical spin states, starting from the Kramers-paired electronic ground state, and find that the induced magnetization exhibits a sharp resonance peak when the applied light frequency is close to half the spin-flipping energy gap. The resonance condition is secondarily affected by the field strength and the pulse width. We suggest that low-energy time reversal broken excitations of insulators can be pursued with a sharp frequency selection as another class of ultrafast phenomena.

中文翻译：

---

时间反向对称绝缘子的法拉第反磁化动力学共振放大

在对磁性单元进行超快控制的背景下，依赖于全光螺旋度的磁性操纵已引起广泛关注。在这里，我们研究了强圆偏振光在时间反转对称绝缘子中的自旋动力学。我们执行实时时变密度函数理论计算以及模型哈密顿分析$莫{\mathrm{小号}}_2$ 和 $\mathrm{w\; ^}{\mathrm{小号}}_2$单层是示例性的自旋轨道耦合时间反转对称绝缘体。我们从Kramers配对电子基态开始追踪动态自旋态的演化，发现当施加的光频率接近自旋翻转能隙的一半时，感应的磁化强度表现出尖锐的共振峰。其次，谐振条件受场强和脉冲宽度的影响。我们建议，可以通过尖锐的频率选择来追求绝缘子的低能量时间反转破坏激励，这是另一类超快现象。