Giant spin-valley polarization and multiple Hall effect in functionalized bismuth monolayers

Zhou, Tong; Zhang, Jiayong; Jiang, Hua; Žutić, Igor; Yang, Zhongqin

doi:10.1038/s41535-018-0113-4

Cited by 56 publications

(28 citation statements)

References 54 publications

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“…Here, the SiC substrate stabilizes the two-dimensional (2D) layer of Bi atoms and shifts the p z orbitals of Bi away from the low-energy sector. As a consequence of this orbital filtering, the low-energy physics of the system is governed by the Bi p x and p y orbitals [7][8][9], which in turn give rise to a large atomic onsite spin-orbit coupling (SOC). Such a mechanism, also predicted for Sb or As on a SiC substrate [10], does not only allow for significantly larger bulk gaps (∼ 0.8 eV) compared to HgTe [3,4,[11][12][13][14] and InAs/GaSb [5] quantum wells (QWs) or WTe 2 [15][16][17] layers, but also compared to other hexagonal layers predicted to exhibit helical states, such as jacutingaite [18], silicene [19][20][21][22], germanene [19,23], stanene [24,25], [(Bi 4 Rh) 3 I] 2+ [26,27], or graphene on WS 2 [28,29].…”

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confidence: 99%

Testing topological protection of edge states in hexagonal quantum spin Hall candidate materials

Domínguez

Scharf

et al. 2018

Phys. Rev. B

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We analyze the detailed structure of topological edge mode protection occurring in hexagonal quantum spin Hall (QSH) materials. We focus on bismuthene, antimonene, and arsenene on a SiC substrate, which, due to their large bulk gap, may offer new opportunities for room-temperature QSH applications. While time reversal symmetry is responsible for the principal symmetry protected character of QSH states, the hexagonal edge terminations yield further aspects of crystal symmetry which affect the topological protection. We show that armchair QSH edge states remain gapless under an in-plane magnetic field in the direction along the edge, a hallmark of their topological crystalline protection. In contrast, an out-of-plane magnetic field opens a gap of the order of a few meV within realistic ranges of the parameters. We use these intriguing signatures of armchair QSH edge states to predict experimentally testable fingerprints of their additional topological crystalline character and their helicity emerging in tunneling spectroscopy and ballistic magnetotransport.

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confidence: 99%

Testing topological protection of edge states in hexagonal quantum spin Hall candidate materials

Domínguez

Scharf

et al. 2018

Phys. Rev. B

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“…2(a)). This magnetism together with the broken space-inversion symmetry in the system may lead to valley polarization effect 30,31 . However, the use of the 3 × 3 supercell in the calculations causes band folding.…”

Section: Resultsmentioning

confidence: 99%

Coexistence of valley polarization and Chern insulating states in MoS2 monolayers with n-p codoping

Wei

Zhang

Zhao

et al. 2020

Sci Rep

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the electronic and topological properties of MoS monolayers with n-p codoping effect are investigated by using first-principles calculations. Two types of the doped Nb atoms play the roles of the p-type and n-type dopants, respectively. The n-p codoping is found inducing a large valley polarization, associated with the strong magnetization induced by the Nb dopants. Interestingly, the system simultaneously owns a perfect Chern insulating band gap opened exactly at the Fermi level. The nontrivial band gap comes from the lifting of the degeneracy of the d xz and d yz orbitals of nb 2 atoms after the spin-orbit coupling is considered. Our work inspires exciting prospects to tune the novel properties of materials with n-p codoping effects. Recently, transition-metal dichalcogenides (TMDs) have been proposed as excellent candidates for electronics, spintronics, and valleytronics materials by manipulating the charge, spin, and valley degrees of freedom in the system 1-4. For example, the experimental realization of valley polarization could be through optical pumping 5,6 in MoS 2 monolayers (MLs) or externally applied magnetic fields 7-9 in WSe 2 and MoSe 2 monolayers. The approach of optical pumping is, however, restricted by the limited carrier lifetimes in dynamical process. And the valley polarization achieved through an external magnetic field is generally quite small. An alternative way to control the valley degree of freedom in TMDs is through magnetic atom doping 10,11 or the proximate effect from magnetic substrates 12. N-p codoping, with both n-type and p-type dopants in one material, has been proved to be an effective strategy to tune the electronic properties 13-15. Ferromagnetic (FM) order was reported in graphene with NiB codoping 13. And quantum anomalous Hall effect was predicted in graphene 14 and Sb 2 Te 3 15 through n-p codoping. In this work, we explore the electronic structures and valleytronics in the MoS 2 monolayer with n-p codoping. Very large valley polarization at the MoS 2 valence bands is obtained, attributed to the imbalance of K and K′ bands aroused by the magnetic Nb dopants. Chern insulating states are also found in the system. The coexistence of valley polarization and Chern insulating effects in the MoS 2 ML with Nb n-p codoping demonstrates that this kind of system has potential applications in not only valleytronics, but also electronics and spintronics, which will greatly facilitate the device integration in practice.

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“…2(e) we observe sharp peaks in the valley region with opposite signs for K and K' which implies the possibility of valley Hall effects in the system. This implies that, when the TeO monolayer is subjected to voltage bias, the electrons from different valleys would experience opposite Lorentz forces leading to electronic motion in opposite directions perpendicular to the drift current thus creating charge-spin segregation making the system a potential quantum valley Hall insulator 50 .…”

Section: (B)(sm))mentioning

confidence: 99%

Functionalized Tellurene; a candidate large-gap 2D Topological Insulator

Sattigeri,

Jha

2021

Preprint

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The discovery of group IV and V elemental Xene's which exhibit topologically non-trivial characters natively in their honeycomb lattice structure (HLS) has led to extensive efforts in realising analogous behaviour in group VI elemental monolayers. Although; it was theoretically concluded that group VI elemental monolayers cannot exist as HLS but recent experimental evidence suggests otherwise. In this letter we report that, HLS of group VI elemental monolayer (such as, Tellurene) can be realised to be dynamically stable when functionzalised with Oxygen. The functionalization leads to, peculiar orbital filtering effects (OFE) and broken spatial inversion symmetry which gives rise to the non-trivial topological character. The exotic quantum behaviour of this system is characterized by, spin-orbit coupling induced large-gap ≈ 0.36 eV with isolated Dirac cone along the edges indicating perspective room temperature spin-transport applications. Further investigations of spin Hall conductivity and the Berry curvatures unravel high conductivity as compared to previously explored Xene's. The non-trivial topological character is quantified in terms of the Z 2 invaraint as ν = 1 and Chern number C = 1. Also, for practical purposes, we report that, hBN/TeO/hBN quantum-wells can be strain engineered to realize a sizable nontrivial gap (≈ 0.11 eV). We finally conclude that, functionalization of group VI elemental monolayer with Oxygen gives rise to, exotic quantum properties which are robust against surface oxidation and degradations while providing viable electronic degrees of freedom for spintronic applications.

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Giant spin-valley polarization and multiple Hall effect in functionalized bismuth monolayers

Cited by 56 publications

References 54 publications

Testing topological protection of edge states in hexagonal quantum spin Hall candidate materials

Testing topological protection of edge states in hexagonal quantum spin Hall candidate materials

Coexistence of valley polarization and Chern insulating states in MoS2 monolayers with n-p codoping

Functionalized Tellurene; a candidate large-gap 2D Topological Insulator

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