Investigation on the Ultrafast Photocurrent Generation in Antimony Telluride (Sb₂Te₃) Nanowire using THz Emission Spectroscopy

Koushik Mondal^1*, Chien-Ming Tu¹, Jiunn-Yuan Lin¹, Chih-Wei Luo^1,2,3

¹Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
²Institute of Physics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
³National Synchrotron Radiation Research Center, Hsinchu, Taiwan

* Presenter:Koushik Mondal, email:koushik@nycu.edu.tw

Over the years antimony telluride (Sb2Te3), a member of topological insulator family is being investigated for their various photo induced phenomena, however, its properties in the nano-structured regime were not well explored. We have investigated the ultrafast photocurrent generation in Sb₂Te₃ nanowire using THz-emission spectroscopy. It is found that these Sb₂Te₃ nanowire with diameter of 80 nm shows 6-times larger THz emission compared with the Sb₂Te₃ single crystal when excited with an 800 nm, fs laser pulse radiation. We have investigated the helicity dependent photocurrent in Sb2Te3 nanowire with different diameter ranging from 10 to 250 nm and isolated the photocurrent coming from the circular photogalvanic effect (CPGE) and linear photogalvanic effect (LPGE). This diameter dependent study shows experimental evidence that such high THz emission coming from the orbital Berry phase effect for the first time. Moreover, this study gives us meaningful insights about the photocurrent generation process in Sb₂Te₃ nanowire that can open up new possibilities for its utilization as THz emitter and in others photonic application.

Keywords: Topological insulator, Sb2Te3 nanowire, THz emission, Berry phase