Resonant reflection at magnetic barriers in quantum wires

Xu, Hengyi; Heinzel, T.; Evaldsson, Martin; Ihnatsenka, S.; Zozoulenko, Igor

doi:10.1103/physrevb.75.205301

Cited by 22 publications

(17 citation statements)

References 35 publications

(73 reference statements)

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“…These types of resonances are well known in conventional two-dimensional semiconductor heterostructures. [49][50][51][52] The Fano resonances in the transmission of graphene nanoribbons have been addressed in Refs. [21][22][23].…”

Section: B Resonant Reflection In Graphene Nanoribbonsmentioning

confidence: 99%

Effect of zigzag and armchair edges on the electronic transport in single-layer and bilayer graphene nanoribbons with defects

2013

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We study electronic transport in monolayer and bilayer graphene with single and many short-range defects focusing on the role of edge termination (zigzag versus armchair). Within the tight-binding approximation, we derive analytical expressions for the transmission amplitude in monolayer graphene nanoribbons with a single short-range defect. The analytical calculations are complemented by exact numerical transport calculations for monolayer and bilayer graphene nanoribbons with a single and many short-range defects and edge disorder. We find that for the case of the zigzag edge termination, both monolayer and bilayer nanoribbons in a single-and few-mode regime remain practically insensitive to defects situated close to the edges. In contrast, the transmission of both armchair monolayer and bilayer nanoribbons is strongly affected by even a small edge defect concentration. This behavior is related to the effective boundary condition at the edges, which, respectively, does not and does couple valleys for zigzag and armchair nanoribbons. In the many-mode regime and for sufficiently high defect concentration, the difference of the transmission between armchair and zigzag nanoribbons diminishes. We also study resonant features (Fano resonances) in monolayer and bilayer nanoribbons in a single-mode regime with a short-range defect. We discuss in detail how an interplay between the defect's position at different sublattices in the ribbons, the defect's distance to the edge, and the structure of the extended states in ribbons with different edge termination influence the width and the energy of Fano resonances.

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Section: B Resonant Reflection In Graphene Nanoribbonsmentioning

confidence: 99%

Effect of zigzag and armchair edges on the electronic transport in single-layer and bilayer graphene nanoribbons with defects

2013

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“…Ideally, the spatial profile of such fields should be extremely sharp along the transport direction and homogeneous in the transverse direction, so that the resulting magnetic barrier might behave as an effective momentum filter, which is necessary to achieve control of the ballistic transmission 4,5 . In addition, strong and sharp barriers generally beget richer transmission characteristics, including the stabilization of confined states within the barrier 6 . The same concept has been proposed following the advent of graphene as a versatile two-dimensional platform for nanoscale electronic devices, with local magnetic barriers being one of several proposed means to confine, guide, and control electron flow [7][8][9][10][11] .…”

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confidence: 99%

Conductance signatures of electron confinement induced by strained nanobubbles in graphene

Bahamon

Park

et al. 2015

Nanoscale

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We investigate the impact of strained nanobubbles on the conductance characteristics of graphene nanoribbons using a combined molecular dynamics -tight-binding simulation scheme. We describe in detail how the conductance, density of states, and current density of zigzag or armchair graphene nanoribbons are modified by the presence of a nanobubble. In particular, we establish that lowenergy electrons can be confined in the vicinity or within the nanobubbles by the delicate interplay between the pseudomagnetic field pattern created by the shape of the bubble, mode mixing, and substrate interaction. The coupling between confined evanescent states and propagating modes can be enhanced under different clamping conditions, which translates into Fano resonances in the conductance traces.The fine control over nanofabrication techniques has not only increased the performance of existing electronic devices 1 , but has also allowed the emergence of concept devices based on the strictly quantum-mechanical properties of electrons. One such proposal is the incorporation of patterned ferromagnetic or superconducting films on two dimensional electron gas (2DEG) structures. Under the right conditions and design parameters, these can be tailored to provide non-homogeneous magnetic fields able to interact strongly with the underlying electrons in the ballistic transport regime 2-5 . Ideally, the spatial profile of such fields should be extremely sharp along the transport direction and homogeneous in the transverse direction, so that the resulting magnetic barrier might behave as an effective momentum filter, which is necessary to achieve control of the ballistic transmission 4,5 . In addition, strong and sharp barriers generally beget richer transmission characteristics, including the stabilization of confined states within the barrier 6 . The same concept has been proposed following the advent of graphene as a versatile two-dimensional platform for nanoscale electronic devices, with local magnetic barriers being one of several proposed means to confine, guide, and control electron flow 7-11 . The need for robust and tunable confinement strategies is more fundamental in graphene electronic devices than in conventional semiconductors: on account of their massless Dirac character, charge carriers in graphene are vulnerable to the phenomenon of Klein tunneling, and cannot be adequately confined by standard electrostatic means, particularly in the ballistic regime. However, even though the search towards achieving control of the electron flow in graphene remains one of the most active research areas when it comes to applications of graphene in the electronics industry, little progress has been made towards this concept of magnetic confinement. This is partly because of the size requirements that call for magnetic barriers that are much smaller than the electronic mean free path, and also because of the need to limit the spatial extent of the magnetic field within regions equally small, since it might be desirable to have portions of t...

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“…This indicates that the resonances are related to the energy spectrum of the dot and not to effects at the individual magnetic barriers as reported in Ref. 24 (note that the resonances investigated there have been obtained for hard wall wires and get suppressed in softer confinement potentials). As the second QWR mode becomes occupied, the character of the resonances switches from transmissive to reflective.…”

Section: Ldos(r; E) = − 1 π Im[g(rr; E)] Where Im Denotes the Imagimentioning

confidence: 53%

Electronic properties of quantum dots formed by magnetic double barriers in quantum wires

Heinzel

Zozoulenko

2011

Phys. Rev. B

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The transport through a quantum wire exposed to two magnetic spikes in series is modeled. We demonstrate that quantum dots can be formed this way which couple to the leads via magnetic barriers. Conceptually, all quantum dot states are accessible by transport experiments. The simulations show Breit-Wigner resonances in the closed regime, while Fano resonances appear as soon as one open transmission channel is present. The system allows one to tune the dots confinement potential from subparabolic to superparabolic by experimentally accessible parameters.Funding Agencies|Heinrich-Heine-Universitat Dusseldorf|

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Resonant reflection at magnetic barriers in quantum wires

Cited by 22 publications

References 35 publications

Effect of zigzag and armchair edges on the electronic transport in single-layer and bilayer graphene nanoribbons with defects

Effect of zigzag and armchair edges on the electronic transport in single-layer and bilayer graphene nanoribbons with defects

Conductance signatures of electron confinement induced by strained nanobubbles in graphene

Electronic properties of quantum dots formed by magnetic double barriers in quantum wires

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