Studied the Ultrafast Dynamics of Topological Insulators Bi2Te3-xSex and Sb2Te3-xSex via Ultrabroadband Mid-infrared Pump-Probe Spectroscopy
Tien-Tien Yeh1*, Wen Hao Lin1, Hideto Shirai2, Takao Fuji2, Cheng-Maw Cheng3, Ku-Ding Tsuei3, Takayoshi Kobayashi1, Fang Cheng Chou4, Marin M. Gospodinov5, Chih-Wei Luo1
1Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
2Institute for Molecular Science, Nagoya, Japan
3National Synchrotron Radiation Research Center, Hsinchu, Taiwan
4Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
5Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia, Bulgaria
* Presenter:Tien-Tien Yeh,
We studied the ultrafast carrier dynamics in topological insulators (TIs) Bi2Te3-xSex and Sb2Te3-xSex (x = 0, 1, 2) by using 800-nm pump and ultrabroadband mid-infrared probe spectroscopy. For detecting the spectra of ultrabroadband mid-infrared light, the chirped-pulse up-conversion technique with four-wave difference frequency generation was applied to convert the sub-10 fs mid-infrared pulse with wavelength 2-50 μm (25-620 meV) to visible region. This report presents the totally different pattern in the transient reflectivity change (ΔR/R) spectra between Bi2Te3-xSex and Sb2Te3-xSex TIs with surface state. The ΔR/R of Bi2Te3-xSex TIs shows the obvious absorption owing to the free carrier absorption, however, that of the Sb2Te3-xSex TIs is dominated by surface carrier absorption.

Keywords: Pump-Probe Spectroscopy, Topological Insulators, Mid-infrared