Title page for etd-0802114-172916


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URN etd-0802114-172916
Author Liang-Zi Yao
Author's Email Address No Public.
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Department Physics
Year 2013
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title Prediction of large gap two-dimensional topological insulators consisting of bilayers of group III elements with Bi
Date of Defense 2014-05-29
Page Count 54
Keyword
  • Topological phase transition
  • First-principles calculations
  • Quantum spin Hall effect
  • 2D topological insulators
  • Electronic structures
  • III-V semiconductor thin films
  • Abstract We use first-principles electronic structure calculations to predict a new class of two-dimensional (2D) topological insulators (TIs) in binary compositions of group III elements (B, Al, Ga, In, and Tl) and bismuth (Bi) in a buckled honeycomb structure. We identify band inversions in pristine GaBi, InBi and TlBi bilayers, with gaps as large as 556 meV, making these materials appropriate suitable for room-temperature applications. Furthermore, we demonstrate the possibility of strain engineering in that the topological phase transition in BBi and AlBi could be driven at ~ 6.6% strain. The buckled structure allows the formation of two different topological edge states in the zigzag and armchair edges. More importantly, isolated Dirac-cone edge states are predicted for armchair edges with the Dirac point lying in the middle of the 2D bulk gap. Room-temperature bulk band gap and isolated Dirac cone allow these states to reach the long-sought topo-logical spin-transport regime. Our findings suggest that the buckled honeycomb struc-ture is a versatile platform for hosting nontrivial topological states and spin-polarized Dirac fermions with the flexibility of chemical and mechanical tunability.
    Advisory Committee
  • Quark Chen - chair
  • Shin-Pon Ju - co-chair
  • Wei-Feng Tsai - co-chair
  • Feng-Chuan Chuang - advisor
  • Files
  • etd-0802114-172916.pdf
  • indicate access worldwide
    Date of Submission 2014-09-02

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