| Summary: | 碩士 === 國立中山大學 === 物理學系研究所 === 103 === We used first-principles electronic structure calculations to predict topological properties in binary compositions of Thallium (Tl) and group V elements in bulks and thin films. Determined by the calculated the topological invariants (Z2), we identified bulk TlBi is a weak topological insulator (TI) and a semimetal. Furthermore, bulk TlP and TlAs are metals and become topological insulator and then semimetal under external strain. As for two-dimensional thin films, we found nontrivial TI phase in two bilayers of hydrogenated TlAs and TlSb, which can withstand a wide range of strain. Additionally, TlN and TlBi could still be driven to nontrivial phase at some strain values. We note energy gaps of all the two-dimensional thin files generally less than 80 meV. Their application at room temperature is pending further studies.
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