Manifestation of a Second Dirac Surface State and Bulk Bands in THz Radiation from Topological Insulators

Chien-Ming Tu, Tien Tien Yeh, Wen Yen Tzeng, Yi Ru Chen, Hsueh Ju Chen, Shin An Ku, Chih-Wei Luo*, Jiunn-Yuan Lin, Kaung-Hsiung Wu, Jenh-Yih Juang, Takayoshi Kobayashi, Cheng Maw Cheng, Ku Ding Tsuei, Helmuth Berger, Raman Sankar, Fang Cheng Chou

*此作品的通信作者

    研究成果: Article同行評審

    19 引文 斯高帕斯(Scopus)

    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 ∼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.

    原文English
    文章編號14128
    頁數8
    期刊Scientific reports
    5
    DOIs
    出版狀態Published - 15 九月 2015

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