Prediction of large gap two-dimensional topological insulators consisting of bilayers of group III elements with Bi

• Main Authors: Liang-Zi Yao, 姚良子
• Other Authors: Feng-Chuan Chuang
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/67018046708897087328

碩士 === 國立中山大學 === 物理學系研究所 === 102 === 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.