Induced spin texture in semiconductor/topological insulator heterostructures

Hutasoit, Jimmy A.; Stãnescu, Tudor D.

doi:10.1103/physrevb.84.085103

Cited by 30 publications

(37 citation statements)

References 29 publications

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“…Interface states have been studied in a number of contexts: TI/graphene 17 , HgTe/CdTe heterostructure 18 , TI/2D semiconductor 19 and for semiconducting thin films on TI 20 . One of the particularly intruiging predictions on the semiconducting/TI interface state is the possibility that nontopological states can acquire spin texture due to their interaction with the topological interface state 20 .…”

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confidence: 99%

Vertical twinning of the Dirac cone at the interface between topological insulators and semiconductors

et al. 2015

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Topological insulators are a new class of matter characterized by the unique electronic properties of an insulating bulk and metallic boundaries arising from non-trivial bulk band topology. While the surfaces of topological insulators have been well studied, the interface between topological insulators and semiconductors may not only be more technologically relevant, but the interaction with non-topological states may fundamentally alter the physics. Here, we present a general model to show that this type of interaction can lead to vertical twinning of the Dirac cone, whereby the hybridized non-spin-degenerate interfacial states cross twice as they span the bulk bandgap. This hybridization leads to spin-momentum locking of non-topological states with either helical (clockwise or anticlockwise) or even anti-helical (negative winding number) spin orientation depending on the parametization of the interaction. Model results are corroborated by first-principles calculations of the technologically relevant Bi2Se3 film van der Waals bound to a Se-treated GaAs substrate.

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confidence: 99%

Vertical twinning of the Dirac cone at the interface between topological insulators and semiconductors

et al. 2015

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“…Insights can be achieved using a p [48]. In this approach the effect of on the graphene spectrum is captur are Pauli matrices acting on the sublattice space, v 1 ≈ 10 6 m/s is the Fermi velocity, and µ 1 is the chemical potential.…”

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confidence: 99%

“…Insights can be achieved using a perturbative approach [48]. In this approach the effect of tunneling processes on the graphene spectrum is captured by the self-energŷ…”

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confidence: 99%

Proximity Effect in Graphene–Topological-Insulator Heterostructures

2014

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We formulate a continuum model to study the low-energy electronic structure of heterostructures formed by graphene on a strong three-dimensional topological insulator (TI) for the case of both commensurate and incommensurate stacking. The incommensurability can be due to a twist angle between graphene and the TI surface or a lattice mismatch between the two systems. We find that the proximity of the TI induces in graphene a strong enhancement of the spin-orbit coupling that can be tuned via the twist angle.The surfaces of strong three-dimensional (3D) topological insulators (TIs) [1] and graphene [2,3] have very similar low-energy electronic structures: the conduction and valence bands touch at isolated points, the Dirac points (DPs), and around these points the fermionic excitations are well described as massless two-dimensional (2D) chiral Dirac fermions for which the phase of a twostate quantum degree of freedom is locked with the momentum direction. However, there are also qualitative differences: (i) in graphene the chirality is associated with the sublattice degree of freedom whereas in a TI surface (TIS) it is associated with the electron spin; (ii) in graphene the number of DPs is even whereas in a TIS it is odd ; (iii) in TIs the electron-phonon scattering is much stronger than that in graphene. Therefore, the transport properties of graphene [4] and TIs are different in significant aspects: in graphene, because the intrinsic spin-orbit (SO) coupling is negligible [5][6][7][8], no quantum spin Hall effect is expected, contrary to the case in a TI; graphene has the highest room-temperature mobility, whereas TIs have very low mobilities. These facts, together with the recent experimental progress [9], motivated us to study graphene-TI heterostructures, in which the proximity to a TI is expected to enhance the SO coupling of graphene and create a novel 2D system with nontrivial spin textures and high, room-temperature, electron mobility. This approach to enhance the SO coupling in graphene appears to be more practical than previously proposed approaches [10] that rely on doping graphene with heavy adatoms.In this work, we study the low-energy electronic structure of heterostructures formed by one sheet of graphene placed on the conducting surface of a 3D TI. Our results show that not only can the proximity of a TIS enhance the SO coupling in graphene and bilayer graphene (BLG), but also that this enhancement can be controlled via the relative rotation, the twist angle, between the graphene lattice and the TI's lattice. The presence of a relative rotation, in general, induces an incommensurate stacking of the graphene and the substrate [11] [12-36]. As a consequence we develop and present a theory that is able to take into account the incommensurability between graphene and the TIS. This cannot be achieved via standard approaches, such as density functional theory [37], and tight-binding models, due to the computational cost of these approaches for incommensurate structures. A continuous model, on the other...

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“…Recently, a number of peculiar quantum phenomena have been discovered in various TI-based heterostructures1415161718192021272829303132333435, such as Majorana fermions induced by the superconducting proximity effect19, topological magnetoelectric effect4, quantized anomalous Hall effect14, and electron reservoir effect of TSS in surface catalysis21. Although the TSS was confirmed to be robust as the TI surface is intruded under diverse conditions provided that time reversal symmetry is preserved212728293031, its properties can be largely modified due to the tunability in the magnitude of interfacial coupling within the heterostructures.…”

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Tuning the vertical location of helical surface states in topological insulator heterostructures via dual-proximity effects

Chen

Sun

et al. 2013

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In integrating topological insulators (TIs) with conventional materials, one crucial issue is how the topological surface states (TSS) will behave in such heterostructures. We use first-principles approaches to establish accurate tunability of the vertical location of the TSS via intriguing dual-proximity effects. By depositing a conventional insulator (CI) overlayer onto a TI substrate (Bi2Se3 or Bi2Te3), we demonstrate that, the TSS can float to the top of the CI film, or stay put at the CI/TI interface, or be pushed down deeper into the otherwise structurally homogeneous TI substrate. These contrasting behaviors imply a rich variety of possible quantum phase transitions in the hybrid systems, dictated by key material-specific properties of the CI. These discoveries lay the foundation for accurate manipulation of the real space properties of TSS in TI heterostructures of diverse technological significance.

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Induced spin texture in semiconductor/topological insulator heterostructures

Cited by 30 publications

References 29 publications

Vertical twinning of the Dirac cone at the interface between topological insulators and semiconductors

Vertical twinning of the Dirac cone at the interface between topological insulators and semiconductors

Proximity Effect in Graphene–Topological-Insulator Heterostructures

Tuning the vertical location of helical surface states in topological insulator heterostructures via dual-proximity effects

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