Topological Dangling Bonds with Large Spin Splitting and Enhanced Spin Polarization on the Surfaces of Bi<sub>2</sub>Se<sub>3</sub>

Lin, Hsin; Das, Tanmoy; Okada, Yoshinori; Boyer, Michael; Wise, W. D.; Tomasik, Michelle; Zhen, Bo; Hudson, Eric; Zhou, Wenwen; Madhavan, Vidya; Ren, Chung Yuan; Ikuta, Hiroshi; Bansil, Arun

doi:10.1021/nl304099x

Cited by 38 publications

(40 citation statements)

References 39 publications

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“…They possess a relatively simple crystal structure composed of stacks of five-atomic-layer-blocks or quintuple blocks (QBs). The QBs are held together by weak van der Waals forces, providing natural cleavage planes without breaking strong bonds, 30 and are theoretically predicted to support only the non-trivial Dirac cone states without the presence of trivial dangling bond states, in agreement with the angle-resolved photoemission spectroscopy (ARPES) results.…”

Section: -29supporting

confidence: 65%

Role of surface termination in realizing well-isolated topological surface states within the bulk band gap inTlBiSe2andTlBiTe2

et al. 2016

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Electronic structures associated with the flat (polar) Se/Te-or Tl-terminated surfaces of TlBiSe2 and TlBiTe2 are predicted to harbor not only the Dirac cone states, but also the trivial dangling bond states near the Fermi energy. However, the latter, trivial states have never been observed in photoemission measurements. In order to address this discrepancy, we have carried out ab-inito calculations for various surfaces of TlBiSe2 and TlBiTe2. A rough nonpolar surface with an equal number of Se/Te and Tl atoms in the surface atomic layer is found to destroy the trivial dangling bond states, leaving only the Dirac cone states in the bulk energy gap. The resulting energy dispersions of the Dirac states are in good accord with the corresponding experimental dispersions in TlBiSe2 as well as TlBiTe2. We also show that in the case of flat, Se terminated, high-index (221) and (112) surfaces of TlBiSe2, the trivial surface states shift energetically below the Dirac node and become well-separated from the Dirac cone states.2

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Section: -29supporting

confidence: 65%

Role of surface termination in realizing well-isolated topological surface states within the bulk band gap inTlBiSe2andTlBiTe2

et al. 2016

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“…7), with only small variations in the fine details of the spectra, regardless of the size, shape, and edge roughness of samples. This provides evidence of the edge state's topologically non-trivial nature 30,31 . The inset is the high-symmetry ARPES cut along the -Y direction aligned in energy with the STS spectrum (acquired from a K-doped sample).…”

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confidence: 76%

Quantum spin Hall state in monolayer 1T'-WTe2

et al. 2017

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A quantum spin Hall (QSH) insulator is a novel twodimensional quantum state of matter that features quantized Hall conductance in the absence of a magnetic field, resulting from topologically protected dissipationless edge states that bridge the energy gap opened by band inversion and strong spin-orbit coupling 1,2 . By investigating the electronic structure of epitaxially grown monolayer 1T'-WTe 2 using angle-resolved photoemission (ARPES) and first-principles calculations, we observe clear signatures of topological band inversion and bandgap opening, which are the hallmarks of a QSH state. Scanning tunnelling microscopy measurements further confirm the correct crystal structure and the existence of a bulk bandgap, and provide evidence for a modified electronic structure near the edge that is consistent with the expectations for a QSH insulator. Our results establish monolayer 1T'-WTe 2 as a new class of QSH insulator with large bandgap in a robust two-dimensional materials family of transition metal dichalcogenides (TMDCs).A two-dimensional (2D) topological insulator (TI), or a quantum spin Hall insulator, is characterized by an insulating bulk and a conductive helical edge state, in which carriers with different spins counter-propagate to realize a geometry-independent edge conductance 2e 2 /h (refs 1,2). The only scattering channel for such helical edge current is back scattering, which is prohibited by time reversal symmetry, making QSH insulators a promising material candidate for spintronic and other applications.The prediction of the QSH effect in HgTe quantum wells sparked intense research efforts to realize the QSH state [3][4][5][6][7][8][9][10][11] . So far only a handful of QSH systems have been fabricated, mostly limited to quantum well structures of three-dimensional (3D) semiconductors such as HgTe/CdTe (ref.3) and InAs/GaSb (ref. 6). Edge conduction consistent with a QSH state has been observed 3,6,12 . However, the behaviour under a magnetic field, where time reversal symmetry is broken, cannot be explained within our current understanding of the QSH effect 13,14 . There have been continued efforts to predict and investigate other material systems to further advance the understanding of this novel quantum phenomenon 5,[7][8][9]15 . So far, it has been difficult to make a robust 2D material with a QSH state, a platform needed for widespread study and application. The small bandgaps exhibited by many candidate systems, as well as their vulnerability to strain, chemical adsorption, and element substitution, make them impractical for advanced spectroscopic studies or applications. For example, a QSH insulator candidate stanene, a monolayer analogue of graphene for tin, grown on Bi 2 Se 3 becomes topologically trivial due to the modification of its band structure by the underlying substrate 11,16 . Free-standing Bi film with 2D bonding on a cleaved surface has shown edge conduction 9 , but its topological nature is still debated 17 . It takes 3D out-of-plane bonding with the substrate and large stra...

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“…The robustness of the gapless surface states has been demonstrated even when the dangling bond states dominate. (Lin, Das, Okada, et al 2013) Topological surface states should be distinguished sharply from the well-known boundary states that arise in normal insulators with a long history in solid-state physics in that the latter type of states are less robust and can be removed by appropriate surface treatment. (Hasan and Kane 2010) First-principles surface state calculations are computationally demanding, and the interpretation of results can be complicated by the spurious gaps resulting from interaction between the top and bottom surfaces of a finite slab.…”

Section: Iid Surface/edge State Computationmentioning

confidence: 99%

Colloquium: Topological band theory

2016

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The first-principles band theory paradigm has been a key player not only in the process of discovering new classes of topologically interesting materials, but also for identifying salient characteristics of topological states, enabling direct and sharpened confrontation between theory and experiment. We begin this review by discussing underpinnings of the topological band theory, which basically involves a layer of analysis and interpretation for assessing topological properties of band structures beyond the standard band theory construct. Methods for evaluating topological invariants are delineated, including crystals without inversion symmetry and interacting systems. The extent to which theoretically predicted properties and protections of topological states have been verified experimentally is discussed, including work on topological crystalline insulators, disorder/interaction driven topological insulators (TIs), topological superconductors, Weyl semimetal phases, and topological phase transitions. Successful strategies for new materials discovery process are outlined. A comprehensive survey of currently predicted 2D and 3D topological materials is provided. This includes binary, ternary and quaternary compounds, transition metal and f-electron materials, Weyl and 3D Dirac semimetals, complex oxides, organometallics, skutterudites and antiperovskites. Also included is the emerging area of 2D atomically thin films beyond graphene of various elements and their alloys, functional thin films, multilayer systems, and ultra-thin films of 3D TIs, all of which hold exciting promise of wide-ranging applications. We conclude by giving a perspective on research directions where further work will broadly benefit the topological materials field.

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Topological Dangling Bonds with Large Spin Splitting and Enhanced Spin Polarization on the Surfaces of Bi₂Se₃

Cited by 38 publications

References 39 publications

Role of surface termination in realizing well-isolated topological surface states within the bulk band gap inTlBiSe2andTlBiTe2

Role of surface termination in realizing well-isolated topological surface states within the bulk band gap inTlBiSe2andTlBiTe2

Quantum spin Hall state in monolayer 1T'-WTe2

Colloquium: Topological band theory

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Topological Dangling Bonds with Large Spin Splitting and Enhanced Spin Polarization on the Surfaces of Bi2Se3

Cited by 38 publications

References 39 publications

Role of surface termination in realizing well-isolated topological surface states within the bulk band gap inTlBiSe2andTlBiTe2

Role of surface termination in realizing well-isolated topological surface states within the bulk band gap inTlBiSe2andTlBiTe2

Quantum spin Hall state in monolayer 1T'-WTe2

Colloquium: Topological band theory

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Topological Dangling Bonds with Large Spin Splitting and Enhanced Spin Polarization on the Surfaces of Bi₂Se₃