破壞塊材反轉對稱在CdTe/HgTe/CdTe結構的量子自旋霍爾物理的影響

Abstract

在本篇論文中，我們探討Dresselhaus自旋軌道作用對CdTe/HgTe/CdTe量子井的拓樸物理之影響，此Dresselhaus自旋軌道作用來自於塊材反轉不對稱。我們也研究以此量子井結構所建構的量子通道的拓樸物理現象。我們研究的出發點為三維的Kane模型，在加上Dresselhaus自旋軌道作用後推導出二維(量子井)及一維(量子通道)的等效哈密頓算符。我們發現系統的拓樸現象並未因Dresselhaus自旋軌道作用的引進而消失，但卻對邊緣態的特性有微妙的影響。具體的影響表現在邊緣態在量子通道中行進的同時發生邊緣態橫向來回移動的現象，是為邊緣切換的現象。此外，在引進位能障後，量子通道的傳輸能譜有Fano共振的結構，且發現可用位能障的高低來調控此結構，Fano結構的出現的同時也驅使邊緣態在穿越位能障的同時完成邊緣切換。本研究詳細分析上述所提之Fano共振的相關物理機制，並獲得一致的結論。

In this thesis, we consider the effects of the Dresselhaus spin orbital interaction (DSOI), a form of breaking inversion symmetry, on the topological physics of a well known topological structure, namely, the CdTe/HgTe/CdTe quantum well. Related system such as a quantum channel formed out of the above quantum well is also considered. Instead of using model 2D Hamiltonian, and quasi-1D Hamiltonian, for the quantum well and quantum channel, respectively, we have calculated these Hamiltonians from the 3D Kane model. This includes our introduction of the DSOI at the 3D Kane model. Our finding is that the DSOI does not destroy the topological physics (the edge states) but has caused intricate effect on the edge states. This is most evident in the case of a quantum channel, when the edge state, under the effect of the DSOI, is caused to exhibit an edge-switching behavior. Furthermore, in the presence of a potential barrier, the transmission exhibits Fano-type characteristics that can be fine-tuned by the barrier height. There is also a feature of forcing the edge-switching to occur in the immediate vicinity of the transmission region. A detail Fano-type process analysis has been performed to confirm the above finding.