Probing spin helical surface states in topological HgTe nanowires

Ziegler, Johannes; Kozlovsky, Raphael; Gorini, Cosimo; Liu, Ming‐Hao; Simon, Weishäupl,; Maier, Hubert; Fischer, R.; Козлов, Д. А.; Квон, З. Д.; Михайлов, Н. Н.; Dvoretsky, S. A.; Richter, Klaus; Weiss, Dieter

doi:10.1103/physrevb.97.035157

Cited by 65 publications

(98 citation statements)

References 40 publications

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“…The dependency on cross section size and shape (e.g., the aspect ratio of a rectangular cross section) and disorder has already been investigated and reported in detail elsewhere and will not be discussed further. 49,[56][57][58] For the Bi 2 Se 3 transport simulations, the direction of uniaxial anisotropy is considered to be perpendicular to the plane (x-z) spanned by the legs of the kink or the Yjunction, in line with the experimental feasibility of these structures. The external magnetic field on the other hand is always considered with in-plane orientation, minimizing its perpendicular component.…”

Section: Magnetotransportmentioning

confidence: 99%

Magnetotransport signatures of three-dimensional topological insulator nanostructures

et al. 2018

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We study the magnetotransport properties of patterned 3D topological insulator nanostructures with several leads, such as kinks or Y-junctions, near the Dirac point with analytical as well as numerical techniques. The interplay of the nanostructure geometry, the external magnetic field and the spin-momentum locking of the topological surface states lead to a richer magnetoconductance phenomenology as compared to straight nanowires. Similar to straight wires, a quantized conductance with perfect transmission across the nanostructure can be realized across a kink when the input and output channels are pierced by a half-integer magnetic flux quantum. Unlike for straight wires, there is an additional requirement depending on the orientation of the external magnetic field. A right-angle kink shows a unique π-periodic magnetoconductance signature as a function of the in-plane angle of the magnetic field. For a Y-junction, the transmission can be perfectly steered to either of the two possible output legs by a proper alignment of the external magnetic field. These magnetotransport signatures offer new ways to explore topological surface states and could be relevant for quantum transport experiments on nanostructures which can be realized with existing fabrication methods.

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Section: Magnetotransportmentioning

confidence: 99%

Magnetotransport signatures of three-dimensional topological insulator nanostructures

et al. 2018

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“…In contrast, strained HgTe-based 3D TIs are characterized by much smaller disorder and higher electron mobility values exceeding 10 5 cm 2 /V·s [14]. Moreover, the highest quality of such systems allowed studying delicate ballistic and interference effects [15,26]. However, these systems have their own shortcomings mainly coming from a zero energy gap in bulk HgTe.…”

Section: Introductionmentioning

confidence: 99%

“…In turn, the requirement of the strain limits the maximum HgTe film thickness to about 100-150 nm because of its relaxation at higher thicknesses (according to [9] and our experience). This fact explains why in the majority of papers devoted to the HgTe-based 3D TIs only 70-100 nm films were studied [3,9,14,15,[26][27][28][29]. On the other hand, studying thicker HgTe films is also desirable because of the higher separation between the surface states, weaker mutual electrostatic coupling and possible hybridization.…”

Section: Introductionmentioning

confidence: 99%

Topological surface states in thick partially relaxed HgTe films

et al. 2019

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Surface states of topological insulators (TIs) have been playing the central role in the majority of outstanding investigations in low-dimensional electron systems for more than 10 years. TIs based on high quality strained HgTe films demonstrate a variety of subtle physical effects. The strain leads to a bulk band gap, but limits a maximum HgTe strained film thickness, and, therefore, the majority of experiments were performed on the films with a thickness of less than 100 nm. Since a spatial separation of topological states is crucial for the study of a single surface response, the HgTe thickness is essential to be increased further. In this work, by combining transport measurements together with capacitance spectroscopy, we performed the analysis of a 200 nm partially relaxed HgTe film. The Drude fit of the classical magnetotransport revealed the ambipolar electron-hole transport with a high electron mobility. The detailed analysis of Shubnikov-de Haas oscillations, both in conductivity and capacitance, allowed us to distinguish three groups of electrons, identified as electrons on top and bottom surfaces and bulk electrons. The indirect bulk energy gap value was found to be close to zero. It was established that the significant gap decrease does not affect the surface states which are found to be well-resolved and spin non-degenerate. The presented techniques allow the investigations of other 3D TIs, regardless of the presence of bulk conductivity.

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“…2(a). The magnetoconductance of such an object is characterized by a non-trivial interplay between two fundamentals of mesoscopic physics: quantum confinement and geometric [Aharonov-Bohm (AB) and Berry] phases [6][7][8][10][11][12].…”

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confidence: 99%

“…Cylindrical TINW in a magnetic field -For later reference we first consider cylindrical TINWs of radius R in longitudinal [6][7][8][10][11][12] or perpendicular [13][14][15][16][17][18][19][20] magnetic fields. They can be described by the 2D surface Dirac Hamiltonian [21] the Hamiltonian simplifies to H = v F (σ z p z + σ y p ϕ ), while the Dirac electron wave functions acquire antiperiodic boundary conditions.…”

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confidence: 99%

Magnetoconductance, Quantum Hall Effect, and Coulomb Blockade in Topological Insulator Nanocones

et al. 2020

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Magnetotransport through cylindrical topological insulator (TI) nanowires is governed by the interplay between quantum confinement and geometric (Aharonov-Bohm and Berry) phases. Here, we argue that the much broader class of TI nanowires with varying radius -for which a homogeneous coaxial magnetic field induces a varying Aharonov-Bohm flux that gives rise to a non-trivial masslike potential along the wire -is accessible by studying its simplest member, a TI nanocone. Such nanocones allow to observe intriguing mesoscopic transport phenomena: While the conductance in a perpendicular magnetic field is quantized due to higher-order topological hinge states, it shows resonant transmission through Dirac Landau levels in a coaxial magnetic field. Furthermore, it may act as a quantum magnetic bottle, confining surface Dirac electrons and leading to Coulomb blockade. We show numerically that the above-mentioned effects occur for experimentally accessible values of system size and magnetic field, suggesting that TI nanocone junctions may serve as building blocks for Dirac electron optics setups.Electronic transport across phase-coherent structures has been a central topic of solid state research ever since the birth of mesoscopic physics some 40 years ago. While the complexity of mesoscopic setups has steadily increased, from the simple gate-defined quantum point contacts of the '80s [1] to elaborate present-day electron optics circuits in semiconductors [2] and graphene [3,4], their structure remains in the vast majority of cases planar -i.e. transport takes place in flat two-dimensional (2D) space. Exceptions to the 2D scenario are samples based on carbon nanotubes and 3D topological insulator (3DTI) nanowires [5][6][7][8]. 3DTIs are bulk band insulators hosting protected 2D surface metallic statesà la Dirac [9]. In mesoscopic nanostructures built out of 3DTIs low-temperature phase-coherent transport takes place on a 2D Dirac metal wrapped around an insulating 3D bulk. As such, it is strongly dependent on a peculiar conjunction of structural (real space) and spectral (reciprocal space) geometrical properties. This has remarkable consequences even for the possibly simplest setup, a topological insulator nanowire (TINW) with constant circular cross section in a coaxial magnetic field, shown in Fig. 2(a). The magnetoconductance of such an object is characterized by a non-trivial interplay between two fundamentals of mesoscopic physics: quantum confinement and geometric [Aharonov-Bohm (AB) and Berry] phases [6][7][8][10][11][12].

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Probing spin helical surface states in topological HgTe nanowires

Cited by 65 publications

References 40 publications

Magnetotransport signatures of three-dimensional topological insulator nanostructures

Magnetotransport signatures of three-dimensional topological insulator nanostructures

Topological surface states in thick partially relaxed HgTe films

Magnetoconductance, Quantum Hall Effect, and Coulomb Blockade in Topological Insulator Nanocones

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