Ji Zhihao, Song Yuna, Song Yiwen, Li Ziyang, Zhang Jingying, Lou Shitao, Zhang Zongzhi, Jin Qingyuan
Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Laboratory of Micro and Nano Photonic Structures (MOE), Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China.
State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China.
ACS Appl Mater Interfaces. 2024 Apr 24. doi: 10.1021/acsami.4c02263.
Topological insulators (TIs) with spin-momentum-locked surface states and considerable spin-to-charge conversion (SCC) efficiency are ideal substitutes for the nonmagnetic layer in the traditional ferromagnetic/nonmagnetic (FM/NM) spintronic terahertz (THz) emitters. Here, the TI/ferrimagnetic structure as an effective polarization tunable THz source is verified by terahertz emission spectroscopy. The emitted THz electric field can be separated into two THz components utilizing their opposite symmetry on pump polarization and the magnetic field. TI not only emits a THz electric field via the linear photogalvanic effect (LPGE) but also serves as the medium of SCC via the inverse Edelstein effect (IEE) in the heterostructure. In addition, the amplitude and polarity of the SCC component can be efficiently manipulated by temperature in our ferrimagnetic TbFeCo layer compared with Co or Fe. Once these two THz components are delicately set orthogonally, an elliptical THz wave is generated by the intrinsic phase difference at the THz frequency range. The feasible control of its polarization and chirality is demonstrated by three means: pump polarization, magnetic field, and temperature. These appealing observations may pave the way for the development of elliptical THz wave emitters and polarization-sensitive THz spectroscopy.
具有自旋动量锁定表面态和可观的自旋到电荷转换（SCC）效率的拓扑绝缘体（TI）是传统铁磁/非磁（FM/NM）自旋电子太赫兹（THz）发射器中非磁层的理想替代品。在此，通过太赫兹发射光谱验证了TI/亚铁磁结构作为一种有效的极化可调太赫兹源。利用发射的太赫兹电场在泵浦极化和磁场方面的相反对称性，可以将其分离为两个太赫兹分量。TI不仅通过线性光电流效应（LPGE）发射太赫兹电场，还在异质结构中通过逆埃德尔斯坦效应（IEE）作为SCC的介质。此外，与Co或Fe相比，在我们的亚铁磁TbFeCo层中，SCC分量的幅度和极性可以通过温度有效地控制。一旦这两个太赫兹分量精确地设置为正交，在太赫兹频率范围内通过固有相位差会产生一个椭圆太赫兹波。通过三种方式证明了对其极化和手性的可行控制：泵浦极化、磁场和温度。这些引人注目的观察结果可能为椭圆太赫兹波发射器和偏振敏感太赫兹光谱学的发展铺平道路。
