Helicity-dependent terahertz radiation from topological insulator Sb2Te3 thin film by femtosecond optical excitation

We report on terahertz radiation from topological insulator (TI) Sb
₂
Te
₃
thin film under ultrafast optical excitation with different helicity. Polarity-reversals of the emitted THz radiation were observed as the helicity of optical pulses reversed. The observed phenomena are coincident with the characteristics of the helicity-dependent photocurrent on TIs. Our work demonstrates the potential applications of surface photocurrents on TIs for opto-spintronics devices.