Helicity-Dependent THz Emission Spectroscopy of Topological Insulators
Chih-Wei Luo1,2*, Chien-Ming Tu3, Yi-Cheng Chen1, Pei-Yu Chuang4, Ming-Yu Lin4, Cheng-Maw Cheng5, Jiunn-Yuan Lin6, Jenh-Yih Juang1, Kaung-Hsiung Wu1, Jung-Chun A. Huang2,4
1Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
2Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei, Taiwan
3Department of Physics, Lund University, Lund, Sweden
4Department of Physics, National Cheng Kung University, Tainan, Taiwan
5National Synchrotron Radiation Research Center, Hsinchu, Taiwan
6Institute of Physics, National Chiao Tung University, Hsinchu, Taiwan
* presenting author:Chih-Wei Luo, email:cwluo@g2.nctu.edu.tw
The exotic properties of topological surface states in topological insulators (TIs) attract much attention due to their potentials in the applications of spintronics. Moreover, the optical coupling of topological surface states can also play an important role in the emerging optospintronics devices. In this study, we show the helicity-dependent THz emissions, originating from the photocurhelicity-dependent rents, in TI Sb2Te3 thin films by ultrafast optical excitation. The polarity of the emitted THz radiation is controlled by both the incident angle and the helicity of ultrafast optical pulses. Employing a decomposition-recombination procedure in time domain (time-domain decomposition-recombination), the individual contributions of circular photogalvanic effect, linear photogalvanic effect and photon drag effect are fully separated. These results provide not only new insights in the optical coupling of topological surface states but also open up new opportunities for applying helicity-dependent THz emission spectroscopic characterization of spintronics devices.

Keywords: THz emission spectroscopy, Topological insulator, Helicity-dependent THz emission