Quantum anomalous Hall and quantum spin-Hall phases in flattened Bi and Sb bilayers

Jin, Kyung-Hwan; Jhi, Seung-Hoon

doi:10.1038/srep08426

Cited by 69 publications

(65 citation statements)

References 47 publications

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“…4b], the system is seen to change from QSH to the QAH phase. This is to be contrasted with the results of a previous study 33 of PL Bi honeycombs with H and N adsorption where the critical point was reached only at c N = 0.65. We find the band gap to be Combined with our earlier findings, 26 where III-Bi honeycombs were predicted to exhibit robust, large-gap QSH phases, the present study further indicates a high degree of tunability of these films in the QAH regime.…”

Section: Resultscontrasting

confidence: 55%

“…In particular, since it has been shown previously that N atoms can support a net magnetic moment when adsorbed on a TI surface, 36 we utilized two types of functionalization: (1) hydrogenation on both sides, and (2) decoration one side with H and with N on the other side. 33 Our earlier work 27 shows that the QSH phase in fully hydrogenated III-Bi honeycombs survives only up to two layers and that the system band gap is reduced as the III-V thin film gets thicker. For this reason, here we focus only on single-layer III-Bi films, which have a larger band gap compared to the multilayer films.…”

Section: Introductionmentioning

confidence: 99%

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Chemically induced large-gap quantum anomalous Hall insulator states in III-Bi honeycombs

et al. 2017

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The search for novel materials with new functionalities and applications potential is continuing to intensify. Quantum anomalous Hall (QAH) effect was recently realized in magnetic topological insulators (TIs) but only at extremely low temperatures. Here, based on our first-principles electronic structure calculations, we predict that chemically functionalized III-Bi honeycombs can support large-gap QAH insulating phases. Specifically, we show that functionalized AlBi and TlBi films harbor QAH insulator phases. GaBi and InBi are identified as semimetals with non-zero Chern number. Remarkably, TlBi exhibits a robust QAH phase with a band gap as large as 466 meV in a buckled honeycomb structure functionalized on one side. Furthermore, the electronic spectrum of a functionalized TlBi nanoribbon with zigzag edge is shown to possess only one chiral edge band crossing the Fermi level within the band gap. Our results suggest that III-Bi honeycombs would provide a new platform for developing potential spintronics applications based on the QAH effect. 1-4 Among the large variety of possible topological phases, quantum anomalous Hall (QAH) insulators 5 have drawn special interest since the QAH state, which supports chiral edge states, is highly suited for spintronics and low-power-consumption electronic applications.6-10 Unlike the quantum Hall state, which relies on the presence of an external magnetic field, the QAH state is realized through the effects of intrinsic spin-orbit coupling (SOC) and intrinsic magnetization in a material. 11 The QAH state was first suggested by Haldane in 1988 using a tight-binding model on a honeycomb lattice, 5 and it has been realized recently in magnetically doped TI thin films.11-15 However, all experimental realizations to date are limited to very low temperatures. It is important, therefore, to search for viable new materials that can support the QAH phase above room temperature, so that the applications potential of these materials can be developed.Theoretical considerations suggest that the QAH effect should be generally achievable in TI thin films via magnetic order (e.g., ferromagnetism), which could be induced through magnetic doping or chemical functionalization.16 Given a quantum spin Hall (QSH) insulator, the QAH phase can be achieved by suppressing one of the two spin-channels via ferromagnetic (FM) ordering. 7,17,18 Many studies have already shown that thin films of elements of groups IV,19,20

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Section: Resultscontrasting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Chemically induced large-gap quantum anomalous Hall insulator states in III-Bi honeycombs

et al. 2017

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“…For example, the functionalized Bi-bilayers have been intensively studied with reports of large nontrivial band gaps for various functional groups (such as -H, -F, -Cl, -Br, -I [183][184][185][186][187], and -CH 3 [187]). However, filtering of the p z -orbital has given different results.…”

Section: Functionalized Honeycomb Lattices Of Group-v Elementsmentioning

confidence: 99%

Topological phases in two-dimensional materials: a review

Ren¹,

2016

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Topological phases with insulating bulk and gapless surface or edge modes have attracted much attention because of their fundamental physics implications and potential applications in dissipationless electronics and spintronics. In this review, we mainly focus on the recent progress in the engineering of topologically nontrivial phases (such as Z2 topological insulators, quantum anomalous Hall effects, quantum valley Hall effects etc.) in two-dimensional material systems, including quantum wells, atomic crystal layers of elements from group III to group VII, and the transition metal compounds.

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“…In particular, the Bi bilayer has been studied extensively as it exhibits various topological phases upon structural and chemical modification [22,23]. The Bi bilayer grown on 3D TI substrates is a real system where the 1D helical edge state is observed explicitly [24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Band structure engineering of topological insulator heterojunctions

2016

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We investigate the topological surface states in heterostructures formed from a three-dimensional topological insulator (TI) and a two-dimensional insulating thin film, using first-principles calculations and the tight-binding method. Utilizing a single Bi or Sb bilayer on top of the topological insulators Bi 2 Se 3 , Bi 2 Te 3 , Bi 2 Te 2 Se, and Sb 2 Te 3 , we find that the surface states evolve in very peculiar but predictable ways. We show that strong hybridization between the bilayer and TI substrates causes the topological surface states to migrate to the top bilayer. It is found that the difference in the work function of constituent layers, which determines the band alignment and the strength of hybridization, governs the character of newly emerged Dirac states.

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Quantum anomalous Hall and quantum spin-Hall phases in flattened Bi and Sb bilayers

Cited by 69 publications

References 47 publications

Chemically induced large-gap quantum anomalous Hall insulator states in III-Bi honeycombs

Chemically induced large-gap quantum anomalous Hall insulator states in III-Bi honeycombs

Topological phases in two-dimensional materials: a review

Band structure engineering of topological insulator heterojunctions

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