Full electrical control of charge and spin conductance through interferometry of edge states in topological insulators

Dolcini, Fabrizio

doi:10.1103/physrevb.83.165304

Cited by 107 publications

(142 citation statements)

References 112 publications

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“…We assume, that the length-scale λ QPC , over which the effects of the QPC are non-negligible is small compared to all other relevant system length scales. 36 Therefore the potential of the QPC can be assumed to be point-like. This allows to write down the tunneling amplitudes as…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…Due to TRS, only three processes at a QPC are allowed, namely: (1) a spin-preserving forward scattering, (2) a spin-and edgeflipping forward scattering and (3) a spin-preserving edge-flipping backscattering. The relevant Hamiltonians at the QPC were already investigated in previous works [35][36][37] [for clarity we recall them in App. A].…”

Section: Model and Formalismmentioning

confidence: 99%

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Proposal for an on-demand source of polarized electrons into the edges of a topological insulator

Inhofer

Bercioux

2013

Phys. Rev. B

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We propose a device that allows for the emission of pairs of spin-polarized electrons into the edge-states of a two dimensional topological insulator. Charge and spin emission is achieved using a periodically driven quantum dot weakly coupled to the edge states of the host topological insulator. We present calculations of the emitted time-dependent charge and spin currents of such a dynamical scatterer using the Floquet scattering matrix approach. Experimental signatures of spin-polarized two-particle emission can be found in noise measurements. Here a new form of noise suppression, named Z2-antibunching, is introduced. Additionally, we propose a set-up in which entanglement of the emitted electrons is generated. This entanglement is based on a post-selection procedure and becomes manifest in a violation of a Clauser-Horne-Shimony-Holt inequality.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Section: Model and Formalismmentioning

confidence: 99%

Proposal for an on-demand source of polarized electrons into the edges of a topological insulator

Inhofer

Bercioux

2013

Phys. Rev. B

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“…Two of them rely on spin switching with a magnetic field at a pn-junction [10] or in an AharonovBohm interferometer [11]. Recently it has further been suggested, also within a phenomenological model, that separate gating of the two branches of an AharonovBohm interferometer allows for manipulating charge-and spin-transport [12]. By contrast, our present proposal relies on an electrical operation by gates on a single HgTe constriction, which up to now was only considered for charge current switching [13].…”

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confidence: 99%

Switching Spin and Charge between Edge States in Topological Insulator Constrictions

2011

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We show how the coupling between opposite edge states, which overlap in a constriction made of the topological insulator mercury telluride (HgTe), can be employed both for steering the charge flow into different edge modes and for controlled spin switching. Unlike in a conventional spin transistor, the switching does not rely on a tunable Rashba spin-orbit interaction, but on the energy dependence of the edge state wavefunctions. Based on this mechanism, and supported by extensive numerical transport calculations, we present two different ways to control spin-and charge-currents, depending on the local gating of the constriction, resulting in a high fidelity spin transistor.PACS numbers: 85.75.Hh, 85.35.Ds Since the prediction of a new topological state of matter in graphene [1], materials exhibiting peculiar surface states and acting as topological insulators have attracted wide attention [2]. Shortly after the theoretical proposal for a mercury telluride (HgTe)-based two-dimensional topological insulator [3], the observation of the quantum spin Hall effect [4] and non-local edge transport [5] brought compelling experimental evidence for quantized conductance due to edges states. The transport along the HgTe boundaries can be conveniently explained by an edge channel picture [6]: Two states with opposite spin orientation propagate along opposite device edges in the same direction and thus lead to a quantized conductance of 2e 2 /h. Due to the spatial separation of the spin-states the spin-orbit coupling is suspended, and the system geometry can be employed for spin selection [5].Spin-selectivity is also a crucial element of the DattaDas spin transistor proposal [7], where charge flow is controlled electrically through the gate-dependent Rashba spin orbit interaction [8] (SOI) in a conventional twodimensional semiconductor heterostructure placed in between ferromagnetic contacts. Its realization, however, turns out to be difficult owing to spin relaxation in the semiconductor heterostructure and interfacial effects such as the conductivity mismatch [9] between the different materials. HgTe-based topological insulators appear to be promising candidates for spin processing devices since they also can be gated and exhibit considerable SOI but, on the contrary, are composed of a single material class only. Moreover, the one-dimensional (1d) nature of their edge states suppresses orbital effects present in bulk conductors, leading to high spin polarizations and to a much better (spin) switching quality.To our knowledge there have been only a few proposals for spin-transistors based on two-dimensional topological insulators. Two of them rely on spin switching with a magnetic field at a pn-junction [10] or in an AharonovBohm interferometer [11]. Recently it has further been suggested, also within a phenomenological model, that separate gating of the two branches of an AharonovBohm interferometer allows for manipulating charge-and spin-transport [12]. By contrast, our present proposal relies on an electrical operati...

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“…In the central region of the setup, the two edge states are coupled by electron tunneling. The tunneling Hamiltonian that preserves time-reversal symmetry consists of two terms [29][30][31][32][33][34][35] , H tun =Ĥ p tun +Ĥ f tun , wherê…”

Section: Modelmentioning

confidence: 99%

“…[24][25][26][27] For the helical states, a constriction in the QSH bar causes a local wavefunction overlap 28,29 that is known to yield two types of tunneling processes. [29][30][31][32][33][34][35][36][37][38][39] The first type is the customary spin-preserving (p) process, where an electron tunnels across the junction maintaining its spin orientation, and thereby reversing its group velocity. The second type is less conventional and is a spin-flipping (f ) process, where a tunneling electron reverses its spin orientation maintaining its group velocity: it mainly originates from the interplay between bulk-inversion asymmetry and wavefunction overlap, even in absence of magnetic coupling.…”

Section: Introductionmentioning

confidence: 99%

Noise and current correlations in tunnel junctions of quantum spin Hall edge states

Dolcini

2015

Phys. Rev. B

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The edge channels of two-dimensional topological systems are protected from elastic reflection and are noiseless at low temperature. Yet, noise and cross-correlations can be induced when electron waves partly transmit to the opposite edge via tunneling through a constriction. In particular, in a quantum spin Hall (QSH) system tunnelling occurs via both spin-preserving (p) and spin-flipping (f ) processes, each fulfilling time-reversal symmetry. We investigate the current correlations of a fourterminal QSH setup in the presence of a tunneling region, both at equilibrium and out-of-equilibrium. We find that, although p and f processes do not commute and the generic current correlation depends on both, under appropriate conditions a direct detection of two types of partition noise is possible. In particular, while the spin-preserving partitioning can be probed for any arbitrary tunnel junction with a specific configuration of terminal biases, the spin-flipping partitioning can be directly detected only under suitably designed setups and conditions. We describe two setups where these conditions can be fulfilled, and both types of partitioning can be detected and controlled.

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Full electrical control of charge and spin conductance through interferometry of edge states in topological insulators

Cited by 107 publications

References 112 publications

Proposal for an on-demand source of polarized electrons into the edges of a topological insulator

Proposal for an on-demand source of polarized electrons into the edges of a topological insulator

Switching Spin and Charge between Edge States in Topological Insulator Constrictions

Noise and current correlations in tunnel junctions of quantum spin Hall edge states

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