论文标题
铁磁拓扑绝缘子表面上的自旋泵诱导的非线性电流
Spin-Pumping-Induced Non-Linear Electric Current on the Surface of a Ferromagnetic Topological Insulator
论文作者
论文摘要
我们研究了三维拓扑绝缘子与铁磁体（即铁磁性拓扑绝缘子）杂交的三维拓扑绝缘子表面上的电流。为此，我们建立了微观形式主义，并使用Keldysh Green的功能方法来构建扰动理论。我们分析了如何通过交换相互作用和外部AC磁场产生的电流，这是铁磁共振的驱动力以及自旋泵送。该机制如下。首先，铁磁共振是驱动的，并出现了零摩肌磁杆。这是从饱和磁化指向平行于铁磁共振的进动轴的波动。在此之后，旋转泵是零momentum木棒是自旋的载体。通过交换相互作用和磁化的旋转的零momentum木元素和拓扑绝缘子表面状态夫妻被转移到其上。由于自旋摩托锁定，转移的自旋转换为拓扑绝缘体表面状态的动量，导致产生垂直于铁磁共振的倾向轴的电流产生。它在外部AC磁场的幅度上是二次的，而与交换相互作用的强度是线性的。相关的电压由零巨木元素的光谱描述。 AC磁场中自旋泵浦诱导的电流的非线性以及交换性相互作用强度中的线性反映，即铁磁性拓扑绝缘器的表面具有高性能通过磁控制产生电荷电流的功能。
We investigate the spin-pumping-induced electric current on the surface of a three-dimensional topological insulator hybridized with a ferromagnet, namely, ferromagnetic topological insulator. In order to do this, we establish the microscopic formalism and construct the perturbation theory using a Keldysh Green's function approach. We analyze how this electric current is generated by an exchange interaction and an external ac magnetic field, which is the driving force of ferromagnetic resonance as well as the spin pumping. The mechanism is as follows. First, the ferromagnetic resonance is driven and a zero-momentum magnon emerges. It is the fluctuation from the saturation magnetization pointing parallel to the precession axis of the ferromagnetic resonance. After then, the spin pumping is generated with the zero-momentum magnon being the carrier of spin. The zero-momentum magnon and the topological insulator surface state couples through the exchange interaction and the spin carried by the magnon is transferred to it. Owing to the spin-momentum locking, the transferred spin is converted into the momentum of topological insulator surface state leading to the generation of electric current flowing perpendicular to the precession axis of the ferromagnetic resonance. It is quadratic in the amplitude of external ac magnetic field whereas it is linear to the strength of the exchange interaction. The associated electric voltage is described by the spectrum of zero-momentum magnon. The non-linearity of spin-pumping-induced electric current in the ac magnetic field as well as the linearity in the exchange-interaction strength reflects that the surface of ferromagnetic topological insulator has a high-performing functionality of generating the electric charge current by magnetic controlling.
