Abstract
Adequately understanding band inversion mechanism, one of the significant representations of topological phase, has substantial implications for design and regulation of topological insulators (TIs). Here, by identifying an unconventional band inversion, we propose an intrinsic quantum spin Hall (QSH) effect in iodinated group-V binary (ABI2) monolayers with a bulk gap as large as 0.409 eV, guaranteeing its viable application at room temperature. The nontrivial topological characters, which can be established by explicit demonstration of Z2 invariant and gapless helical edge states, are derived from the band inversion of antibonding states of px,y orbitals at the K point. Furthermore, the topological properties are tunable under strain engineering and external electric field, which supplies a route to manipulate the spin/charge conductance of edge states. These findings not only provide a new platform to better understand the underlying origin of QSH effect in functionalized group-V films, but also are highly desirable to design large-gap QSH insulators for practical applications in spintronics.
Highlights
Topological insulators (TIs)[1,2,3], a new quantum state of matter, which can effectively achieve the objective of spintronics by controlling spin configuration and spin current[4, 5], have attracted great research enthusiasm since they were proposed in 2005
In this work, based on first-principles calculations, we propose the simultaneous presence of unconventional band inversion and intrinsic quantum spin Hall (QSH) effect in iodinated group-V binary monolayers (ABI2) which are dynamically and thermally stable at room temperature
We find that the valence bands maximum (VBM) and conduction bands minimum (CBM) of ABI2 monolayers are all fixed at K point, forming a direct band gap (EgSOC)
Summary
Topological insulators (TIs)[1,2,3], a new quantum state of matter, which can effectively achieve the objective of spintronics by controlling spin configuration and spin current[4, 5], have attracted great research enthusiasm since they were proposed in 2005. The topological phase, accompanied with a sufficiently large bulk gap of 0.409 eV, can be identified by the band inversion of antibonding states of px,y orbitals between A and B atoms induced by SOC at K point and explicit confirmation of Z2 invariant, as well as gapless helical edge states Their QSH effect can be modulated by strain engineering and external electric field with tunable bulk gap. The electronically controlled transition between nontrivial and trivial phases in AsBiI2 monolayer can effectively switch spin and charge transports to design topological quantum devices These findings are conducive to propelling the understanding of topological mechanism in group-V films and supporting promising candidates to design spintronic and optoelectronic devices
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