Anisotropic surface transport in topological insulators in proximity to a helical spin density wave

Li, Qiuzi; Ghosh, Parag; Sau, Jay D.; Tewari, Sumanta; Sarma, S. Das

doi:10.1103/physrevb.83.085110

Cited by 20 publications

(19 citation statements)

References 34 publications

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“…Correspondingly, the existence of a solution with ε = 0 implies the existence of another with the property ψ(r) = σ z ψ(r). This is obviously fulfilled for the functions (18) and (19). The solution we found describes the wave functions and the energy spectrum of the states near the point k = 0.…”

Section: The K · P Approach: Low-energy Solutionsupporting

confidence: 53%

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Topological insulator in a helicoidal magnetization field

et al. 2016

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A key feature of topological insulators is the robustness of the electron energy spectrum. At a surface of a topological insulator, Dirac point is protected by the characteristic symmetry of the system. The breaking of the symmetry opens a gap in the energy spectrum. Therefore, topological insulators are very sensitive to magnetic fields, which can open a gap in the electronic spectrum. Concerning "internal" magnetic effects, for example the situation with doped magnetic impurities, is not trivial. A single magnetic impurity is not enough to open the band gap, while in the case of a ferromagnetic chain of deposited magnetic impurities the Dirac point is lifted. However, a much more interesting case is when localized magnetic impurities form a chiral spin order. Our first principle density functional theory calculations have shown that this is the case for Fe deposited on the surface of Bi2Se3 topological insulator. But not only magnetic impurities can form a chiral helicoidal spin texture. An alternative way is to use chiral multiferroics (prototype material is LiCu2O2) that induce a proximity effect. The theoretical approach we present here is valid for both cases. We observed that opposite to a ferromagnetically ordered case, a chiral spin order does not destroy the Dirac point. We also observed that the energy gap appears at the edges of the new Brillouin zone. Another interesting result concerns the spin dynamics. We derived an equation for the spin density dynamics with a spin current and relaxation terms. We have shown that the motion of the conductance electron generates a magnetic torque and exerts a certain force on the helicoidal texture.

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Section: The K · P Approach: Low-energy Solutionsupporting

confidence: 53%

“…where C 1 and C 2 are constants determined by normalization. The matrix of the HamiltonianĤ in the basis of functions (18) and (19) isĤ…”

Section: The K · P Approach: Low-energy Solutionmentioning

confidence: 99%

Topological insulator in a helicoidal magnetization field

et al. 2016

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“…Beside the ARPES and band structure calculations, there has been a growing number of experiments 97–124 and theoretical studies 125–187 devoted to helical transport in 3DTI materials. Like in the QSHIs, the surface charge carriers in 3DTIs are characterized by a well‐defined spin helicity, i.e., the locking of the spin and momentum directions.…”

Section: Introductionmentioning

confidence: 99%

Spin‐helical transport in normal and superconducting topological insulators

Tkachov

Hankiewicz

2013

Physica Status Solidi (b)

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31 85141In a topological insulator (TI) the character of electron transport varies from insulating in the interior of the material to metallic near its surface. Unlike, however, ordinary metals, conducting surface states in TIs are topologically protected and characterized by spin helicity whereby the direction of the electron spin is locked to the momentum direction. In this paper we review selected topics regarding recent theoretical and experimental work on electron transport and related phenomena in two-dimensional (2D) and three-dimensional (3D) TIs.The review provides a focused introductory discussion of the quantum spin Hall effect in HgTe quantum wells as well as transport properties of 3DTIs such as surface weak antilocalization, the half-integer quantum Hall effect, s þ p-wave induced superconductivity, superconducting Klein tunneling, topological Andreev bound states and related Majorana midgap states. These properties of TIs are of practical interest, guiding the search for the routes towards topological spin electronics. 1 Introduction The situation when a material behaves as a metal in terms of its electric conductivity and, at the same time, as an insulator in terms of its band structure is extremely unconventional from the viewpoint of the standard classification of solids. That is why the recent discovery of a class of such materials -topological insulators (TIs) -has generated much interest (see e.g., reviews [1,2]). The dual properties of the TIs are especially well pronounced in two-dimensional (2D) systems which are also known as quantum spin-Hall insulators (QSHIs) [3][4][5][6][7]. In QSHIs, the metallic electric conduction is associated with propagating states that occur only near the sample edges, while the conduction in the interior is suppressed by a band gap like in ordinary band insulators. These edge states originate from intrinsic spin-orbit (SO) coupling and are profoundly different from those appearing in quantum Hall systems in a strong perpendicular magnetic field [8,9]. The key distinction lies in the role of the time reversal symmetry. In the QSHIs the SO coupling preserves the time-reversal symmetry, resulting in a pair of counter-propagating channels on the same edge as opposed to one-way directed (chiral) edge states in quantum Hall systems. Remarkably, the spin and momentum directions of the two QSHI edge channels are locked in the opposite ways so that these states are characterized by opposite spin helicities and orthogonal

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“…Li et al 70 studied transport in topological insulators in the neighborhood of a helical spin density wave. The nontrivial magnetic structure results in a spatially localized breakdown of time reversal symmetry on the TI surface.…”

Section: Ti Metalmentioning

confidence: 99%

Transport in three-dimensional topological insulators: Theory and experiment

Culcer

2012

Physica E: Low-dimensional Systems and Nanostructures

143

140

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This article reviews recent theoretical and experimental work on transport due to the surface states of three-dimensional topological insulators. The theoretical focus is on longitudinal transport in the presence of an electric field, including Boltzmann transport, quantum corrections and weak localization, as well as longitudinal and Hall transport in the presence of both electric and magnetic fields and/or magnetizations. Special attention is paid to transport at finite doping, to the π-Berry phase, which leads to the absence of backscattering, Klein tunneling and half-quantized Hall response. Signatures of surface states in ordinary transport and magnetotransport are clearly identified. The review also covers transport experiments of the past years, reviewing the initial obscuring of surface transport by bulk transport, and the way transport due to the surface states has increasingly been identified experimentally. Current and likely future experimental challenges are given prominence and the current status of the field is assessed.

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Anisotropic surface transport in topological insulators in proximity to a helical spin density wave

Cited by 20 publications

References 34 publications

Topological insulator in a helicoidal magnetization field

Topological insulator in a helicoidal magnetization field

Spin‐helical transport in normal and superconducting topological insulators

Transport in three-dimensional topological insulators: Theory and experiment

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