Proximity-induced spin-orbit coupling in graphene/
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Bi</mml:mi><mml:mrow><mml:mn>1.5</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi>Sb</mml:mi><mml:mrow><mml:mn>0.5</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi>Te</mml:mi><mml:mrow><mml:mn>1.7</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi>Se</mml:mi><mml:mrow><mml:mn>1.3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>
 heterostructures

Jafarpisheh, Shaham; Cummings, Aron W.; Watanabe, Kenji; Taniguchi, Takashi; Beschoten, Bernd; Stampfer, Christoph

doi:10.1103/physrevb.98.241402

Cited by 20 publications

(34 citation statements)

References 62 publications

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“…[ 44,45 ] Carrying out these types of measurements in a nonlocal detection scheme makes it possible to separate the contribution of the bulk and solely characterize the topologically protected surface states. [ 46 ]…”

Section: Exfoliationmentioning

confidence: 99%

Reducing the Impact of Bulk Doping on Transport Properties of Bi‐Based 3D Topological Insulators

Jafarpisheh

Janßen

et al. 2020

Physica Status Solidi (b)

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The observation of helical surface states in Bi-based three-dimentional topological insulators has been a challenge since their theoretical prediction. The main issue raises when the Fermi level shifts deep into the bulk conduction band due to the unintentional doping. This results in a metallic conduction of the bulk which dominates the transport measurements and hinders the probing of the surface states in these experiments. In this study, we investigate various strategies to reduce the residual doping in Bi-based topological insulators. Flakes of Bi2Se3 and Bi1.5Sb0.5Te1.7Se1.3 are grown by physical vapor deposition and their structural and electronic properties are compared to mechanically exfoliated flakes. Using Raman spectroscopy, we explore the role of the substrate in this process and present the optimal conditions for the fabrication of high quality crystals. Despite of this improvement, we show that the vapor phase deposited flakes still suffer from structural disorder which leads to the residual n-type doping of the bulk. Using magneto-measurements we show that exfoliated flakes have better electrical properties and are thus more promising for the probing of surface states. arXiv:2001.04368v2 [cond-mat.mes-hall]

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Section: Exfoliationmentioning

confidence: 99%

Reducing the Impact of Bulk Doping on Transport Properties of Bi‐Based 3D Topological Insulators

Jafarpisheh

Janßen

et al. 2020

Physica Status Solidi (b)

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“…[ 55 ] To compensate this effect and to bring the Dirac states to the Fermi level, the multicompositional topological insulator crystals

{Bi}_{2 - x} {Sb}_{x} {Te}_{3 - y} {Se}_{y}

are considered. [ 25,57,58 ] Depending on the numbers x and y , the defect doping can be counteracted and bulk transport can be suppressed. Of course, the formation of the Dirac states depends also on the number of QLs, [ 8–60 ] because for thin samples the surface state wave functions still interact with each other through the bulk, such that gapless surface states are absent.…”

Section: Monolayer Graphene In Proximity To Bi2se3 and Bi2te3mentioning

confidence: 99%

“…There have already been numerous studies considering graphene/topological insulator bilayers, [ 23–39 ] in which two different kinds of Dirac electrons are simultaneously present. More specifically, it is possible to grow high‐quality topological insulators such as Bi 2 Se 3 epitaxially layer‐by‐layer on graphene, with small defect density.…”

Section: Introductionmentioning

confidence: 99%

“…Similar to transition‐metal dichalcogenides, [ 17,18 ] topological insulators strongly enhance the negligible intrinsic SOC of the graphene Dirac states from 10 μeV, [ 11,41,42 ] by two orders of magnitude to about 1 meV. [ 23,25,43 ] The proximity‐induced SOC in graphene is giant, drastically reducing spin relaxation times, and of valley‐Zeeman type, leading to giant spin relaxation anisotropies. [ 23,44 ] Such graphene/topological insulator bilayers are ideal for the interaction of topological surface states, with in‐plane spin‐momentum locking, and the proximity‐induced spin‐orbit fields in graphene.…”

Section: Introductionmentioning

confidence: 99%

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Heterostructures of Graphene and Topological Insulators Bi₂Se₃, Bi₂Te₃, and Sb₂Te₃

Zollner

Fabian

2020

Physica Status Solidi (b)

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Prototypical 3D topological insulators of the Bi2Se3 family provide a beautiful example of the appearance of the surface states inside the bulk bandgap caused by spin‐orbit coupling‐induced topology. The surface states are protected against backscattering by time reversal symmetry, and exhibit spin‐momentum locking whereby the electron spin is polarized perpendicular to the momentum, typically in the plane of the surface. In contrast, graphene is a prototypical 2D material, with negligible spin‐orbit coupling. When graphene is placed on the surface of a topological insulator, giant spin‐orbit coupling is induced by the proximity effect, enabling interesting novel electronic properties of its Dirac electrons. A detailed theoretical study of the proximity effects of monolayer graphene and topological insulators Bi2Se3, Bi2Te3, and Sb2Te3 is presented, and the appearance of the qualitatively new spin‐orbit splittings, well described by a phenomenological Hamiltonian, is elucidated by analyzing the orbital decomposition of the involved band structures. This should be useful for building microscopic models of the proximity effects between the surfaces of the topological insulators and graphene.

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“…Since each QL is about 1 nm in thickness, these materials are in between the 2D and 3D regime, depending on how many QLs one investigates. Nevertheless, they are important for practical applications 34 , due to their topologically protected 35,36 and well conducting surface states 37 , and for proximity induced phenomena [38][39][40][41] , since strong SOC is present. When the topological insulators act as a substrate, the 2D regime (1-2 QLs) is sufficient, as proximity effects are of short range nature.…”

Section: Introductionmentioning

confidence: 99%

Single and bilayer graphene on the topological insulator Bi2Se3 : Electronic and spin-orbit properties from first principles

Zollner

Fabian

2019

Phys. Rev. B

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We present a detailed study of the electronic and spin-orbit properties of single and bilayer graphene in proximity to the topological insulator Bi2Se3. Our approach is based on first-principles calculations, combined with symmetry derived model Hamiltonians that capture the low-energy band properties. We consider single and bilayer graphene on 1-3 quintuple layers of Bi2Se3 and extract orbital and proximity induced spin-orbit coupling (SOC) parameters. We find that graphene gets significantly hole doped (350 meV), but the linear dispersion is preserved. The proximity induced SOC parameters are about 1 meV in magnitude, and are of valley-Zeeman type. The induced SOC depends weakly on the number of quintuple layers of Bi2Se3. We also study the effect of a transverse electric field, that is applied across heterostructures of single and bilayer graphene above 1 quintuple layer of Bi2Se3. Our results show that band offsets, as well as proximity induced SOC parameters can be tuned by the field. Most interesting is the case of bilayer graphene, in which the band gap, originating from the intrinsic dipole of the heterostructure, can be closed and reopened again, with inverted band character. The switching of the strong proximity SOC from the conduction to the valence band realizes a spin-orbit valve. Additonally, we find a giant increase of the proximity induced SOC of about 200%, when we decrease the interlayer distance between graphene and Bi2Se3 by only 10%. Finally, for a different substrate material Bi2Te2Se, band offsets are significantly different, with the graphene Dirac point located at the Fermi level, while the induced SOC strength stays similar in magnitude compared to the Bi2Se3 substrate.

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Proximity-induced spin-orbit coupling in graphene/ Bi1.5Sb0.5Te1.7Se1.3 heterostructures

Cited by 20 publications

References 62 publications

Reducing the Impact of Bulk Doping on Transport Properties of Bi‐Based 3D Topological Insulators

Reducing the Impact of Bulk Doping on Transport Properties of Bi‐Based 3D Topological Insulators

Heterostructures of Graphene and Topological Insulators Bi₂Se₃, Bi₂Te₃, and Sb₂Te₃

Single and bilayer graphene on the topological insulator Bi2Se3 : Electronic and spin-orbit properties from first principles

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Proximity-induced spin-orbit coupling in graphene/ Bi1.5Sb0.5Te1.7Se1.3 heterostructures

Cited by 20 publications

References 62 publications

Reducing the Impact of Bulk Doping on Transport Properties of Bi‐Based 3D Topological Insulators

Reducing the Impact of Bulk Doping on Transport Properties of Bi‐Based 3D Topological Insulators

Heterostructures of Graphene and Topological Insulators Bi2Se3, Bi2Te3, and Sb2Te3

Single and bilayer graphene on the topological insulator Bi2Se3 : Electronic and spin-orbit properties from first principles

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Heterostructures of Graphene and Topological Insulators Bi₂Se₃, Bi₂Te₃, and Sb₂Te₃