Abstract
Group III-V films are of great importance for their potential application in spintronics and quantum computing. Search for two-dimensional III-V films with a nontrivial large-gap are quite crucial for the realization of dissipationless transport edge channels using quantum spin Hall (QSH) effects. Here we use first-principles calculations to predict a class of large-gap QSH insulators in functionalized TlSb monolayers (TlSbX2; (X = H, F, Cl, Br, I)), with sizable bulk gaps as large as 0.22 ~ 0.40 eV. The QSH state is identified by Z2 topological invariant together with helical edge states induced by spin-orbit coupling (SOC). Noticeably, the inverted band gap in the nontrivial states can be effectively tuned by the electric field and strain. Additionally, these films on BN substrate also maintain a nontrivial QSH state, which harbors a Dirac cone lying within the band gap. These findings may shed new light in future design and fabrication of QSH insulators based on two-dimensional honeycomb lattices in spintronics.
Highlights
Chemical functionalization of 2D materials is an effective way to realize quantum spin Hall (QSH) state with desirable large-gaps
These findings may provide a new platform to design large-gap QSH insulator based on group III-V films, which is important for device application in spintronics
On the basis of first-principles calculations, we predict a class of new QSH insulator of TlSbX2 (X = H, F, Cl, Br, I) films, with a sizable bulk gap (0.22 ~ 0.40 eV), allowing for viable applications in spintronic devices
Summary
Large-Gap Quantum Spin Hall received: 30 October 2015 accepted: 22 January 2016 Published: 17 February 2016. The common feature of these materials is that they all own 2D honeycomb-like crystal structures, indicating that 2D hexagonal lattice could be an excellent cradle to breed QSH insulators with SOC These large-gap QSH insulators are essential for realizing many exotic phenomena and for fabricating new quantum devices that can operate at room temperature. A single pair of topologically protected helical edge states is established for these systems with the Dirac point locating in the bulk gap, and the odd numbers of crossings between edge states and Fermi level prove the nontrivial nature of these TlSbX2 films These findings may provide a new platform to design large-gap QSH insulator based on group III-V films, which is important for device application in spintronics
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