拓樸絕緣體碲化銻薄膜之兆赫波輻射光譜學研究

Study of Terahertz Emission Spectroscopy in Topological Insulator Sb2Te3 thin film

陳奕成(Yi- Cheng Chen)

指導教授 ： 羅志偉

國立交通大學/理學院/電子物理系所/碩士(2016年)

摘要

在這本論文中，我們利用超快雷射激發拓樸絕緣體碲化銻薄膜，
使其輻射具有旋光相依性的兆赫波。我們藉由不同偏振光入射下，觀
察到兆赫波的極性會有翻轉之現象。這個翻轉的現象，和旋光相依性
的光電流行為是非常吻合的。接著採用兆赫波時域波形的分離及重組
方法，將原本混合在一起的三個物理機制個別分離出來，這三個物理
機制分別為圓偏振光致自旋電流效應、線偏振光致自旋電流效應、光
子牽引效應。此外，我們可以從時間解析與角度解析光電子能譜的光
激載子動力學结果得到相對應的瞬時電流，在考慮遠場下，此瞬時電
流所產生的電磁輻射與我們的實驗結果一致。
最後，我們的研究不僅證明了拓樸絕緣體的表面態可輻射出具有
旋光相依性的兆赫波，而且本論文的成果也進一步說明了兆赫波輻射
光譜學是研究自旋電子學相關主題的新利器。

關鍵字

兆赫波 ； 拓樸絕緣體

並列摘要

In this thesis, we show the helicity-dependent terahertz emissions from topological insulator (TI) Sb2Te3 thin films by ultrafast optical excitation. We observed the polarity-reversal of the emitted THz radiation as the helicity of optical pulses reverses. The observed phenomenon is consistent with the characteristics of the helicity-dependent photocurrent on TIs. Employing a decomposition-recombination procedure in time domain, the individual contributions of circular photogalvanic effect, linear photogalvanic effect and photon drag effect are revealed completely. Additionally, based on the Tr-ARPES results and considering transient-current radiation as well as far-field diffraction, our results are the same as that from Tr-ARPES results.
Finally, our results not only demonstrate that helicity-dependent THz emission originated from topological insulator surface states can be manipulated by ultrafast optical pulses but also pave a way towards applications of THz emission spectroscopy on spintronics.

並列關鍵字

Terahertz ； Topological Insulator

參考文獻

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