標題: Manifestation of a Second Dirac Surface State and Bulk Bands in THz Radiation from Topological Insulators
作者: Tu, Chien-Ming
Yeh, Tien-Tien
Tzeng, Wen-Yen
Chen, Yi-Ru
Chen, Hsueh-Ju
Ku, Shin-An
Luo, Chih-Wei
Lin, Jiunn-Yuan
Wu, Kaung-Hsiung
Juang, Jenh-Yih
Kobayashi, Takayoshi
Cheng, Cheng-Maw
Tsuei, Ku-Ding
Berger, Helmuth
Sankar, Raman
Chou, Fang-Cheng
物理研究所
電機學院
電機工程學系
Institute of Physics
College of Electrical and Computer Engineering
Department of Electrical and Computer Engineering
公開日期: 15-Sep-2015
摘要: Topological insulators (TIs) are interesting quantum matters that have a narrow bandgap for bulk and a Dirac-cone-like conducting surface state (SS). The recent discovered second Dirac surface state (SS) and bulk bands (BBs) located similar to 1.5 eV above the first SS are important for optical coupling in TIs. Here, we report on the time-domain measurements of THz radiation generated from TIs n-type Cu0.02Bi2Se3 and p-type Bi2Te3 single crystals by ultrafast optical pulse excitation. The observed polarity-reversal of the THz pulse originated from transient current is unusual, and cannot be reconciled with the photo-Dember effect. The second SS and BBs are found to be indispensable for the explanation of the unusual phenomenon. Thanks to the existence of the second SS and BBs, TIs manifest an effective wide band gap in THz generation. The present study demonstrates that time-domain THz spectroscopy provide rich information of the optical coupling and the electronic structure of TIs.
URI: http://dx.doi.org/10.1038/srep14128
http://hdl.handle.net/11536/128276
ISSN: 2045-2322
DOI: 10.1038/srep14128
期刊: SCIENTIFIC REPORTS
Volume: 5
起始頁: 0
結束頁: 0
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