Imaging backscattering through impurity-induced antidots in quantum Hall constrictions

Paradiso, Nicola; Heun, S.; Roddaro, Stefano; Biasiol, G.; Sorba, L.; Venturelli, Davide; Taddei, F.; Giovannetti, Vittorio; Beltram, Fabio

doi:10.1103/physrevb.86.085326

Cited by 16 publications

(11 citation statements)

References 29 publications

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“…We make use of SGM and experimentally directly determine whether impurity is present or not near a given constriction. SGM has proven to be extremely sensitive in probing the potential landscape of two-dimensional electron systems [28][29][30]. This high sensitivity in detecting conductance variations makes the SGM technique an ideal tool to investigate the effect of potential imperfections on the conductance of constrictions.…”

Section: Introductionmentioning

confidence: 99%

Scanning Gate Imaging of Quantum Point Contacts and the Origin of the 0.7 Anomaly

Iagallo¹,

Paradiso²,

Roddaro³

et al. 2014

Extended Abstracts of the 2014 International Conference on Solid State Devices and Materials

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The origin of the anomalous transport feature appearing at conductance G ≈ 0.7 x (2e 2 /h) in quasi-1D ballistic devices − the so-called 0.7 anomaly − represents a long standing puzzle. Several mechanisms were proposed to explain it, but a general consensus has not been achieved. Proposed explanations are based on quantum interference, Kondo effect, Wigner crystallization, and more. A key open issue is whether point defects that can occur in these low-dimensional devices are the physical cause behind this conductance anomaly. Here we adopt a scanning gate microscopy technique to map individual impurity positions in several quasi-1D constrictions and correlate these with conductance characteristics. Our data demonstrate that the 0.7 anomaly can be observed irrespective of the presence of localized defects, and we conclude that the 0.7 anomaly is a fundamental property of low-dimensional systems.

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Section: Introductionmentioning

confidence: 99%

Scanning Gate Imaging of Quantum Point Contacts and the Origin of the 0.7 Anomaly

Iagallo¹,

Paradiso²,

Roddaro³

et al. 2014

Extended Abstracts of the 2014 International Conference on Solid State Devices and Materials

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“…16 The SGM set-up allows us to explore the quantum Hall edge channel physics through a different and rarely used, non-uniform gating potential and provides full control over the edge channels, which can be made to interact, equilibrate, and/or backscatter as one sees fit. [17][18][19] As a consequence of the spatial variation of the tip potential, we are able to spatially separate copropagating channels inside the uniform Hall bar, which leads to new, intricate junctions that have not been reported before. Finally, we demonstrate the ability to accurately simulate our experiments through tight binding simulations.…”

Section: Introductionmentioning

confidence: 72%

Manipulating quantum Hall edge channels in graphene through scanning gate microscopy

et al. 2017

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We show evidence of the backscattering of quantum Hall edge channels in a narrow graphene Hall bar, induced by the gating effect of the conducting tip of a Scanning Gate Microscope, which we can position with nanometer precision. We show full control over the edge channels and are able, due to the spatial variation of the tip potential, to separate co-propagating edge channels in the Hall bar, creating junctions between regions of different charge carrier density, that have not been observed in devices based on top-or split-gates. The solution of the corresponding quantum scattering problem is presented to substantiate these results, and possible follow-up experiments are discussed.

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“…In addition to quantum dots, SGM has also proved useful in studying a variety of other, bulk properties of graphene. [12][13][14] SGM has previously been used to study localized charge states-quantum dots-in carbon nanotubes, 15 graphene, 16,17 GaAs-based heterostructures, [18][19][20] and InAs-based quantum wires, 21 among other systems. The prototypical result of a scanning measurement of quantum dots is a map of conductance as a function of tip position displaying sets of rings of enhanced conductance.…”

Section: Introductionmentioning

confidence: 99%

Scanning gate microscopy of localized states in wide graphene constrictions

et al. 2013

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In graphene nanoconstrictions, charge puddles due to substrate-induced potential inhomogeneities can form quantum dots. We use a scanning gate microscope to probe a short, wide graphene constriction and observe a set of ring-shaped resonances in maps of the graphene conductance as a function of the local potential perturbation, a signature of quantum dot-mediated transport. By varying the scanning tip height and applied tip voltage, we observe the screening effect of the nearby graphene. Introducing a simple capacitive model to account for screening, we model the conduction of the graphene constriction and how the tip gates the quantum dots. We identify the locations of some of the quantum dots and extract their parameters.

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Imaging backscattering through impurity-induced antidots in quantum Hall constrictions

Cited by 16 publications

References 29 publications

Scanning Gate Imaging of Quantum Point Contacts and the Origin of the 0.7 Anomaly

Scanning Gate Imaging of Quantum Point Contacts and the Origin of the 0.7 Anomaly

Manipulating quantum Hall edge channels in graphene through scanning gate microscopy

Scanning gate microscopy of localized states in wide graphene constrictions

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