Khusyainov Dinar, Ovcharenko Sergei, Gaponov Mikhail, Buryakov Arseniy, Klimov Alexey, Tiercelin Nicolas, Pernod Philippe, Nozdrin Vadim, Mishina Elena, Sigov Alexander, Preobrazhensky Vladimir
MIREA - Russian Technological University, Moscow, Russia, 119454.
Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, UMR 8520 -IEMN, 59000, Lille, France.
Sci Rep. 2021 Jan 12;11(1):697. doi: 10.1038/s41598-020-80781-5.
Polarization of electromagnetic waves plays an extremely important role in interaction of radiation with matter. In particular, interaction of polarized waves with ordered matter strongly depends on orientation and symmetry of vibrations of chemical bonds in crystals. In quantum technologies, the polarization of photons is considered as a "degree of freedom", which is one of the main parameters that ensure efficient quantum computing. However, even for visible light, polarization control is in most cases separated from light emission. In this paper, we report on a new type of polarization control, implemented directly in a spintronic terahertz emitter. The principle of control, realized by a weak magnetic field at room temperature, is based on a spin-reorientation transition (SRT) in an intermetallic heterostructure TbCo/FeCo with uniaxial in-plane magnetic anisotropy. SRT is implemented under magnetic field of variable strength but of a fixed direction, orthogonal to the easy magnetization axis. Variation of the magnetic field strength in the angular (canted) phase of the SRT causes magnetization rotation without changing its magnitude. The charge current excited by the spin-to-charge conversion is orthogonal to the magnetization. As a result, THz polarization rotates synchronously with magnetization when magnetic field strength changes. Importantly, the radiation intensity does not change in this case. Control of polarization by SRT is applicable regardless of the spintronic mechanism of the THz emission, provided that the polarization direction is determined by the magnetic moment orientation. The results obtained open the prospect for the development of the SRT approach for THz emission control.
电磁波的极化在辐射与物质的相互作用中起着极其重要的作用。特别是，极化波与有序物质的相互作用强烈依赖于晶体中化学键振动的取向和对称性。在量子技术中，光子的极化被视为一种“自由度”，它是确保高效量子计算的主要参数之一。然而，即使对于可见光，在大多数情况下极化控制与光发射是分开的。在本文中，我们报道了一种直接在自旋电子太赫兹发射器中实现的新型极化控制。这种控制原理是在室温下通过弱磁场实现的，它基于具有单轴面内磁各向异性的金属间异质结构TbCo/FeCo中的自旋重取向转变（SRT）。SRT是在强度可变但方向固定的磁场下实现的，该磁场与易磁化轴正交。在SRT的角（倾斜）相中改变磁场强度会导致磁化强度旋转而不改变其大小。由自旋到电荷转换激发的电荷电流与磁化强度正交。结果，当磁场强度变化时，太赫兹极化与磁化强度同步旋转。重要的是，在这种情况下辐射强度不变。只要极化方向由磁矩取向决定，通过SRT进行的极化控制适用于任何太赫兹发射的自旋电子机制。所获得的结果为开发用于太赫兹发射控制的SRT方法开辟了前景。
