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首頁> 外文學(xué)位 >Exotic surface states of topological insulators and topological superconductors - quasiparticle scattering in the surface of 3d topological insulators and realization of majorana fermions.
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Exotic surface states of topological insulators and topological superconductors - quasiparticle scattering in the surface of 3d topological insulators and realization of majorana fermions.

機譯：拓撲絕緣子和拓撲超導(dǎo)體的外來表面狀態(tài)-3d拓撲絕緣子表面中的準粒子散射和馬約拉那費米子的實現(xiàn)。

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摘要

In this thesis, three works on topological insulators (TIs) and topological superconductors (TSCs) will be reported. First, we study the quasiparticle interference (QPI) patterns caused by scattering off nonmagnetic, magnetic point impurities, and edge impurities, separately, in a two dimensional helical liquid, which describes the surface states of a topological insulator. The unique features associated with hexagonal warping effects are identified in the QPI patterns of charge density with nonmagnetic impurities and spin density with magnetic impurities. The symmetry properties of the QPI patterns can be used to determine the symmetry of microscopic models. The Friedel oscillation is calculated for edge impurities and the decay of the oscillation is not universal, strongly depending on Fermi energy. Some discrepancies between our theoretical results and current experimental observations are discussed. Second, we theoretically propose a manipulation scheme for the one-dimensional Majorana fermions emerged in a topological insulator-ferromagnet-superconductor (TI-FM-SC) heterostructure by engineering its magnetic configurations. We demonstrate that the existence of the Majorana edge modes critically depends on the combination of the directions and magnitudes of spin polarization on all surfaces of the TI, and that a model describing the states on only one surface is insufficient. In particular, as shown by analytic calculations, the number, the positions and the chirality of these edge modes corresponding to various topological SC phases can be engineered in this way as well. Third, a new propose for the realization of Majorana zero-modes in 1D silicene domain wall is reported. By applying inhomogeneous perpendicular electric fields to the silicene sheet, 1D domain wall -- which supports midgap states -- can be generated. Plus the appreciable spin-orbit couplings (SOC) due to the buckled structure of silicene, the domain wall can be a good analog of a 1D wire made of semiconductors with strong SOC, which provides us a new access to the realization of Majorana zero-modes in 1D systems.
機譯：在這篇論文中，將報道有關(guān)拓撲絕緣體（TI）和拓撲超導(dǎo)體（TSC）的三篇著作。首先，我們分別研究了二維螺旋液體中由非磁性，磁性雜質(zhì)和邊緣雜質(zhì)的散射所引起的準粒子干擾（QPI）模式，該液體描述了拓撲絕緣體的表面狀態(tài)。在具有非磁性雜質(zhì)的電荷密度和具有磁性雜質(zhì)的自旋密度的QPI模式中，可以識別出與六邊形翹曲效應(yīng)相關(guān)的獨特特征。 QPI模式的對稱性可用于確定微觀模型的對稱性。弗里德爾振蕩是針對邊緣雜質(zhì)計算的，并且振蕩的衰減并不普遍，這在很大程度上取決于費米能量。討論了我們的理論結(jié)果與當(dāng)前的實驗觀察結(jié)果之間的一些差異。其次，我們從理論上提出了一種通過工程化其磁結(jié)構(gòu)來解決拓撲絕緣子-鐵磁體-超導(dǎo)體（TI-FM-SC）異質(zhì)結(jié)構(gòu)中出現(xiàn)的一維Majorana費米子的處理方案。我們證明了Majorana邊緣模式的存在嚴重取決于TI所有表面上自旋極化的方向和大小的組合，并且僅描述一個表面上的狀態(tài)的模型是不夠的。特別地，如通過解析計算所示，也可以以這種方式設(shè)計與各種拓撲SC相相對應(yīng)的這些邊緣模式的數(shù)量，位置和手性。第三，報道了在一維硅晶疇壁中實現(xiàn)馬約拉納零模的新提議。通過對硅片施加不均勻的垂直電場，可以生成一維疇壁（支持中隙態(tài)）。再加上由于硅的彎曲結(jié)構(gòu)引起的明顯的自旋軌道耦合（SOC），疇壁可以很好地模擬由具有強SOC的半導(dǎo)體制成的一維線，這為我們提供了實現(xiàn)馬約拉納零零位的新途徑一維系統(tǒng)中的各種模式。

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  • 作者

    Zhou, Xiaoting.;

  • 作者單位

    Purdue University.;

  • 授予單位 Purdue University.;
  • 學(xué)科 Physics General.;Physics Condensed Matter.
  • 學(xué)位 Ph.D.
  • 年度 2013
  • 頁碼 81 p.
  • 總頁數(shù) 81
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類
  • 關(guān)鍵詞

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