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Crystal field effect induced topological crystalline insulators in monolayer IV-VI semiconductors.

Authors
Type
Published Article
Journal
Nano Letters
1530-6984
Publisher
American Chemical Society
Publication Date
Volume
15
Issue
4
Pages
2657–2661
Identifiers
DOI: 10.1021/acs.nanolett.5b00308
PMID: 25741907
Source
Medline
Keywords
  • Iv−Vi Semiconductors
  • Topological Crystalline Insulators
  • Atomically Thin Materials
  • Crystal Field Effect

Abstract

Two-dimensional (2D) topological crystalline insulators (TCIs) were recently predicted in thin films of the SnTe class of IV-VI semiconductors, which can host metallic edge states protected by mirror symmetry. As thickness decreases, quantum confinement effect will increase and surpass the inverted gap below a critical thickness, turning TCIs into normal insulators. Surprisingly, based on first-principles calculations, here we demonstrate that (001) monolayers of rocksalt IV-VI semiconductors XY (X = Ge, Sn, Pb and Y = S, Se, Te) are 2D TCIs with the fundamental band gap as large as 260 meV in monolayer PbTe. This unexpected nontrivial topological phase stems from the strong crystal field effect in the monolayer, which lifts the degeneracy between p(x,y) and p(z) orbitals and leads to band inversion between cation pz and anion px,y orbitals. This crystal field effect induced topological phase offers a new strategy to find and design other atomically thin 2D topological materials.

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