Advanced Photonics, 2023, 5 (5): 056006, Published Online: Sep. 18, 2023  

Nonrelativistic and nonmagnetic terahertz-wave generation via ultrafast current control in anisotropic conductive heterostructures

Author Affiliations
1 Fudan University, State Key Laboratory of Surface Physics, Department of Physics, Shanghai, China
2 Fudan University, Key Laboratory of Micro and Nano Photonic Structures, Shanghai, China
3 Shanghai Research Center for Quantum Sciences, Shanghai, China
4 Beijing Normal University, Center for Advanced Quantum Studies, Department of Physics, Beijing, China
5 Fudan University, Institute for Nanoelectronic Devices and Quantum Computing, Shanghai, China
Precise and ultrafast control over photo-induced charge currents across nanoscale interfaces could lead to important applications in energy harvesting, ultrafast electronics, and coherent terahertz sources. Recent studies have shown that several relativistic mechanisms, including inverse spin-Hall effect, inverse Rashba–Edelstein effect, and inverse spin-orbit-torque effect, can convert longitudinally injected spin-polarized currents from magnetic materials to transverse charge currents, thereby harnessing these currents for terahertz generation. However, these mechanisms typically require external magnetic fields and exhibit limitations in terms of spin-polarization rates and efficiencies of relativistic spin-to-charge conversion. We present a nonrelativistic and nonmagnetic mechanism that directly utilizes the photoexcited high-density charge currents across the interface. We demonstrate that the electrical anisotropy of conductive oxides RuO2 and IrO2 can effectively deflect injected charge currents to the transverse direction, resulting in efficient and broadband terahertz radiation. Importantly, this mechanism has the potential to offer much higher conversion efficiency compared to previous methods, as conductive materials with large electrical anisotropy are readily available, whereas further increasing the spin-Hall angle of heavy-metal materials would be challenging. Our findings offer exciting possibilities for directly utilizing these photoexcited high-density currents across metallic interfaces for ultrafast electronics and terahertz spectroscopy.

Sheng Zhang, Yongwei Cui, Shunjia Wang, Haoran Chen, Yaxin Liu, Wentao Qin, Tongyang Guan, Chuanshan Tian, Zhe Yuan, Lei Zhou, Yizheng Wu, Zhensheng Tao. Nonrelativistic and nonmagnetic terahertz-wave generation via ultrafast current control in anisotropic conductive heterostructures[J]. Advanced Photonics, 2023, 5(5): 056006.

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