High Chern number quantum anomalous Hall phases in single-layer graphene with Haldane orbital coupling

Chen, Tsung-Wei; Xiao, Zhifeng; Chiou, Dah-Wei; Guo, Guang‐Yu

doi:10.1103/physrevb.84.165453

Cited by 40 publications

(39 citation statements)

References 68 publications

(79 reference statements)

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“…Because of these edge states, the Cu 2 S/MnSe heterostructure has great potential for the fabrication of a dissipationless, 100% spin-polarized, and highspeed spintronic devices and is superior to the Chern insulators with no spin polarization or partially spin-polarized edge states. 19,21,22 It is also important to note that the E F in this system lies in the nontrivial band gap, enabling improvements in the experimental observations.…”

Section: Resultsmentioning

confidence: 97%

Novel Chern insulators with half-metallic edge states

et al. 2018

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The central target of spintronics research is to achieve flexible control of highly efficient and spin-polarized electronic currents. Based on first-principles calculations and k·p models, we demonstrate that Cu 2 S/MnSe heterostructures are a novel type of Chern insulators with half-metallic chiral edge states and a very high Fermi velocity (0.87 × 10 6 m s − 1 ). The full spin-polarization of the edge states is found to be robust against the tuning of the chemical potential. Unlike the mechanisms reported previously, this heterostructure has quadratic bands with a normal band order, that is, the p/d-like band is below the s-like band. Charge transfer between the Cu 2 S moiety and the substrate results in variation in the occupied bands, which together with spin-orbit coupling, triggers the appearance of the topological state in the system. These results imply that numerous ordinary semiconductors with normal band order may convert into Chern insulators with half-metallic chiral edge states through this mechanism, providing a strategy to find a rich variety of materials for dissipationless, 100% spin-polarized and high-speed spintronic devices.

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Section: Resultsmentioning

confidence: 97%

Novel Chern insulators with half-metallic edge states

et al. 2018

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“…In previous studies of the QAHE in the context of graphene, [20][21][22][23][24] an extended Kane-Mele model 4 was employed with an additional Rashba term. The effective Rashba spinorbit interaction originates from the combination of intrinsic SOC and potential gradient perpendicular to the honeycomb lattice plane which breaks the inversion symmetry, and can be created by, e.g., applying a finite electric field perpendicular to the honeycomb plane 25 or imposing a finite curvature of the honeycomb sheet.…”

Section: A P Z Orbitalsmentioning

confidence: 99%

“…Sublattice staggering as found in silicene 17 is too small to induce significant variation of the electronic structure, thus the simplified four-band model considering only the π bands is good enough to account for the topological phase transitions in graphene-related systems. [20][21][22][23] However, for Bi(111) bilayer and its derivatives, all three p orbitals reside in the same energy scale, the hybridization between them is strongly enhanced due to buckling, and the strength of SOC is orders of magnitude larger as compared to that of carbon or silicon atoms. Therefore, rich physics with competing orbital and spin degrees of freedom is expected in the latter case.…”

Section: B S Orbitalsmentioning

confidence: 99%

“…18,19 In the past, a lot of work has been done based on the extended Kane-Mele model 4 in the context of graphene. 9,[20][21][22][23][24] In these studies, only the σ band of the p z orbitals is considered, with key terms to induce topological nontriviality being effective projected spin-orbit and Rashba spin-orbit interactions, arising from second-order perturbative processes. 25 The strength of intrinsic atomic spin-orbit coupling of carbon is limited, although it can be enhanced in fine-tuned systems.…”

Section: Introductionmentioning

confidence: 99%

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Engineering quantum anomalous Hall phases with orbital and spin degrees of freedom

et al. 2013

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Combining tight-binding models and first-principles calculations, we investigate the quantum anomalous Hall (QAH) effect induced by intrinsic spin-orbit coupling (SOC) in buckled honeycomb lattice with sp orbitals in an external exchange field. Detailed analysis reveals that nontrivial topological properties can arise utilizing not only spin but also orbital degrees of freedom in the strong SOC limit, when the bands acquire nonzero Chern numbers upon undergoing the so-called orbital purification. As a prototype of a buckled honeycomb lattice with strong SOC we choose the Bi(111) bilayer, analyzing its topological properties in detail. In particular, we show the emergence of several QAH phases upon spin exchange of the Chern numbers as a function of SOC strength and magnitude of the exchange field. Interestingly, we observe that in one of such phases, namely, in the quantum spin Chern insulator phase, the quantized charge and spin Hall conductivities coexist. We consider the possibility of tuning the SOC strength in the Bi bilayer via alloying with isoelectronic Sb, and speculate that exotic properties could be expected in such an alloyed system owing to the competition of the topological properties of its constituents. Finally, we demonstrate that 3d dopants can be used to induce a sizable exchange field in the Bi(111) bilayer, resulting in nontrivial Chern insulator properties.

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“…Interestingly, the two edge states are on the same edge with the spin-up state moving right and the spin-down state moving left, i.e., they form the helical quantum spin Hall-like edge states. Since the time-reversal symmetry is broken here, the ZNR can be considered as the pseudo-quantum spin Hall insulator25. Finally, we notice that as the width of the ZNRs is increased from n = 10 to n = 17, the calculated energy bands remain more or less unchanged.…”

Section: Resultsmentioning

confidence: 85%

Tunable magnetic states on the zigzag edges of hydrogenated and halogenated group-IV nanoribbons

Wang

Hsu

Huang

et al. 2016

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The magnetic and electronic properties of hydrogenated and halogenated group-IV zigzag nanoribbons (ZNRs) are investigated by first-principles density functional calculations. Fascinatingly, we find that all the ZNRs have magnetic edges with a rich variety of electronic and magnetic properties tunable by selecting the parent and passivating elements as well as controlling the magnetization direction and external strain. In particular, the electric property of the edge band structure can be tuned from the conducting to insulating with a band gap up to 0.7 eV. The last controllability would allow us to develop magnetic on-off nano-switches. Furthermore, ZNRs such as SiI, Ge, GeI and SnH, have fully spin-polarized metallic edge states and thus are promising materials for spintronics. The calculated magnetocrystalline anisotropy energy can be as large as ~9 meV/edge-site, being 2×103 time greater than that of bulk Ni and Fe (~5 μeV/atom), and thus has great potential for high density magneto-electric data-storage devices. Finally, the calculated exchange coupling strength and thus magnetic transition temperature increases as the applied strain goes from −5% to 5%. Our findings thus show that these ZNRs would have exciting applications in next-generation electronic and spintronic nano-devices.

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High Chern number quantum anomalous Hall phases in single-layer graphene with Haldane orbital coupling

Cited by 40 publications

References 68 publications

Novel Chern insulators with half-metallic edge states

Novel Chern insulators with half-metallic edge states

Engineering quantum anomalous Hall phases with orbital and spin degrees of freedom

Tunable magnetic states on the zigzag edges of hydrogenated and halogenated group-IV nanoribbons

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