Energy spectrum and broken spin-surface locking in topological insulator quantum dots

We study the electronic and transport properties of a topological insulator nanowire including selective magnetic doping of its surfaces. We use a model which is appropriate to describe materials like Bi 2 Se 3 within a k · p approximation and consider nanowires with a rectangular geometry. Within this model the magnetic doping at the (111) surfaces induces a Zeeman field which opens a gap at the Dirac cones corresponding to the surface states. For obtaining the transport properties in a two terminal configuration we use a recursive Green's function method based on a tight-binding model which is obtained by discretizing the original continuous model. For the case of uniform magnetization of two opposite nanowire (111) surfaces we show that the conductance can switch from a quantized value of e 2 /h (when the magnetizations are equal) to a very small value (when they are opposite). We also analyze the case of nonuniform magnetizations in which the Zeeman field on the two opposite surfaces change sign at the middle of the wire. For this case we find that conduction by resonant tunneling through a chiral state bound at the middle of the wire is possible. The resonant level position can be tuned by imposing an Aharonov-Bohm flux through the nanowire cross section.

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“…. Analogous expression have been obtained for TI wires with cylindrical geometry [34,35]. In we plot the quantum wire surface band structure, Eq.…”

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confidence: 99%

Transport in selectively magnetically doped topological insulator wires

2015

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“…However, as detailed in Refs. [34,[41][42][43][44][45][46], the results of such calculations are well reproduced by a simple description in terms of effectively 2D massless Dirac fermions wrapped onto the surface of the device, subject to the constraint that spin is oriented tangentially to the surface and perpendicularly to the momentum at any point. The full surface state solution includes a radial part describing a rapid exponential decay into the bulk of the nanowire.…”

Section: A Modelmentioning

confidence: 71%

Majorana qubits in a topological insulator nanoribbon architecture

et al. 2017

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We describe designs for the realization of topological Majorana qubits in terms of proximitized topological insulator nanoribbons pierced by a uniform axial magnetic field. This platform holds promise for particularly robust Majorana bound states, with easily manipulable inter-state couplings. We propose proof-of-principle experiments for initializing, manipulating, and reading out Majorana box qubits defined in floating devices dominated by charging effects. We argue that the platform offers design advantages which make it particularly suitable for extension to qubit network structures realizing a Majorana surface code.

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“…48 and in a TI system with a different geometry in Ref. 40. We will see below that the parameter α leads to some non-trivial effects, namely, scattering at the edge and the appearance of states localized at the edge; such effects therefore do not appear in Ref.…”

Section: B Edge Between Two Surfacesmentioning

confidence: 95%

Edge states of a three-dimensional topological insulator

Deb

Soori

Sen

2014

J. Phys.: Condens. Matter

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We use the bulk Hamiltonian for a three-dimensional topological insulator such as Bi2Se3 to study the states which appear on its various surfaces and along the edge between two surfaces. We use both analytical methods based on the surface Hamiltonians (which are derived from the bulk Hamiltonian) and numerical methods based on a lattice discretization of the bulk Hamiltonian. We find that the application of a potential barrier along an edge can give rise to states localized at that edge. These states have an unusual energy-momentum dispersion which can be controlled by applying a potential along the edge; in particular, the velocity of these states can be tuned to zero. The scattering and conductance across the edge is studied as a function of the edge potential. We show that a magnetic field in a particular direction can also give rise to zero energy states on certain edges. We point out possible experimental ways of looking for the various edge states.

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Energy spectrum and broken spin-surface locking in topological insulator quantum dots

Cited by 38 publications

References 33 publications

Transport in selectively magnetically doped topological insulator wires

Transport in selectively magnetically doped topological insulator wires

Majorana qubits in a topological insulator nanoribbon architecture

Edge states of a three-dimensional topological insulator

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