利用拓樸絕緣體摻銅硒化鉍晶體產生兆赫波輻射

Abstract

最近，硒化鉍晶體被發現為一種三維的拓樸絕緣體，在本論文中，我們利用本研究群所建立之兆赫波產生技術，研究摻銅及未摻雜硒化鉍晶體所產生的兆赫波特性。研究中發現，兆赫波訊號大小和樣品的載子濃度有很密切的關連性，由摻銅的硒化鉍晶體(載子濃度~1018 cm-3)所產生的兆赫波訊號比未摻雜的硒化鉍晶體(載子濃度~1019 cm-3)大上十倍。除此之外，本論文也針對硒化鉍晶體產生兆赫波的機制進行討論，並分析其與拓樸絕緣體表面態之間的關係。

Bi2Se3 with highly thermoelectric power is, recently, known for its properties of three-dimensional topological insulator. In this thesis, we report that the terahertz wave can be generated from the surface of Bi2Se3 and Cu-doped Bi2Se3 single crystals by the femtosecond optical pumping pulses at 800 nm. Furthermore, the terahertz output power is strongly dependent on the carrier concentrations. The THz wave generated from the Cu-doped Bi2Se3 with carrier concentration ~1018 cm-3 is nearly ten times higher than that from the pure Bi2Se3 with carrier concentration ~1019 cm-3. The THz generation mechanism on the pure, Cu-doped Bi2Se3 and even the correlation between THz wave generation and the surface state of topological insulator will be discussed in this thesis.