Helicity-dependent Terahertz Emission from Topological Material SrCd₂As_xSb_2-x single crystals

Ying Kuan Ko^1*, Xin-Yun Chang¹, Yan-Cheng Ko¹, Po-Wei Gong¹, Yi-Cheng Cheng¹, Pei-Tsung Yang¹, Jiun-Haw Chu², Cheng-Chien Chen³, Chih-Wei Luo¹, Jiunn-Yuan Lin⁴, Chien-Ming Tu^1,5,6

¹Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
²Department of Physics, University of Washington, Seattle, WA, USA
³Department of Physics, University of Alabama at Birmingham, Birmingham, AL, USA
⁴Institute of Physics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
⁵Undergraduate Degree Program of Systems Engineering and Technology, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
⁶Chung Cheng Institute of Technology, National Defense University, Taoyuan, Taiwan

* Presenter:Ying Kuan Ko, email:kentko78@gmail.com

Abstract: We report on helicity-dependent terahertz emission from topological material SrCd₂As_xSb_2-x single crystals under ultrafast optical excitation with different polarization. For SrCd₂Sb₂ (x = 0), nonzero term for circular photogalvanic effect (CPGE) was extracted by a quarter-waveplate (QWP) phase-angle scan (α-scan) in the case of oblique incidence of optical pulses. The observed phenomena agree with spin-polarized photocurrent from the nontrival topological surface state. Our work demonstrates the potential applications of SrCd₂Sb₂ on opto-spintronics devices.

Keywords: Terahertz emission, Topological materials, Spintronics