Magnetic resonances driven by current-induced torques are crucial tools to study magnetic materials but are very limited in frequency and mechanical efficiency. We propose an alternative mechanism, voltage-induced torque, to realize high efficiency in generating high-frequency magnetization dynamics. When a ferromagnet–topological insulator–ferromagnet trilayer heterostructure is operated as an adiabatic quantum motor, voltage-induced torque arises from the adiabatic motion of gapped topological electrons on the two interfaces and act oppositely on the two ferromagnetic layers, which can excite the exchange mode where the two ferromagnetic layers precess with a $\pi$-phase difference. The exchange mode resonance, bearing a much higher frequency than the ferromagnetic resonance, is accompanied by topological charge pumping, leading to a sharp peak in electrical admittance at the resonance point. Because the output current is purely adiabatic while dissipative current vanishes identically, the proposed voltage-driven exchange resonance entails a remarkably high mechanical efficiency close to unity, which is impossible in any current-driven systems.

中文翻译：

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电压驱动交流谐振实现100%机械效率

由电流引起的转矩驱动的磁共振是研究磁性材料的重要工具，但在频率和机械效率方面非常有限。我们提出了一种替代机制，即电压感应转矩，以实现高效率产生高频磁化动力学。当铁磁体-拓扑绝缘体-铁磁体三层异质结构作为绝热量子电机运行时，电压感应扭矩来自两个界面上的带隙拓扑电子的绝热运动，并在两个铁磁层上反向作用，可以激发交换模式其中两个铁磁层以$\pi$- 相位差。具有比铁磁共振高得多的频率的交换模式共振伴随着拓扑电荷泵浦，导致在共振点处的电导纳的尖峰。因为输出电流是纯绝热的，而耗散电流同样消失，所以所提出的电压驱动交换谐振需要非常高的接近于单位的机械效率，这在任何电流驱动系统中都是不可能的。