Stable branched electron flow

Braem, Beat A.; Gold, Carolin; Hennel, Szymon; Röösli, Marc P.; Berl, Matthias; Dietsche, W.; Wegscheider, Werner; Ensslin, Klaus; Ihn, Thomas

doi:10.1088/1367-2630/aad068

Cited by 16 publications

(30 citation statements)

References 21 publications

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“…That is, the probability of being reflected back through the QPC is independent of the position of the tip. Detailed numerical calculations [7] have recently confirmed the approximate validity of the proportionality between the local trajectory density in the absence of the tip and the tip-induced conductance change in the case of a smooth disordered potential. In order to be consistent with the semi-classical approximation, the QPC is assimilated to a point source and we simply assume that the angular distribution of the emerging classical trajectories is smooth.…”

Section: Branch Formation and Stability In A Toy Modelmentioning

confidence: 76%

“…In this work we have provided an explanation for the robust stability of branches in the scanning gate response of two-dimensional electron gases with smooth disorder, with respect to a change in the Fermi energy observed in Ref. [7]. We have done so by first invoking a toy model for the formation and the energy stability of these branches, which we have argued is sufficient to capture all of the observed features of branching in more refined models and in the experiments.…”

Section: Discussionmentioning

confidence: 96%

“…Over the last two decades, developments in the field of scanning gate microscopy (SGM) have allowed for the detailed investigation of nanostructured devices based on a two-dimensional electron gas (2DEG) where different confining geometries can be defined; among them, a quantum point contact (QPC) [1][2][3][4][5][6][7], a quantum billiard [8,9], a ballistic ring [10,11], an electron wave-guide [12], and a tunable electron cavity [13]. The change in electrical conductance of the nanostructure under the effect of a charged atomic force microscope raster scanning above the surface of the device results in a mapping that provides a characterization of the nature of the device well beyond that of a conventional electrical transport measurement [14].…”

Section: Introductionmentioning

confidence: 99%

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Energy stability of branching in the scanning gate response of two-dimensional electron gases with smooth disorder

2019

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The branched pattern typically observed through the scanning gate microscopy (SGM) of two dimensional electron gases in the presence of weak, smooth disorder has recently been found to be robust against a very large shift in the Fermi energy of the electron gas. We propose a toy model, where the potential landscape reduces to a single localized feature, that makes it possible to recast the understanding of branch formation through the effect of caustics in an appropriate set of classical trajectories, and it is simple enough to allow for a quantitative analysis of the energy and spatial dependence of the branches. We find the energy stability to be extremely generic, as it rests only upon the assumptions of weak disorder, weak scattering, and the proportionality of the SGM response to the density of classical electron trajectories. Therefore, the robustness against changes of the electron's Fermi energy remains when adopting progressively realistic models of smooth disorder.Journal reference: Phys. Rev. B 100, 155435 (2019) arXiv:1904.07777v2 [cond-mat.mes-hall]

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Section: Branch Formation and Stability In A Toy Modelmentioning

confidence: 76%

Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Energy stability of branching in the scanning gate response of two-dimensional electron gases with smooth disorder

2019

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“…Indeed, even in the range where Mott's relation (1) is valid, deducing the TSGM image S(x tip , y tip ) from the SGM G(x tip , y tip ) would require a knowledge of how the transmission evolves with the chemical potential (∂G/∂µ). Most of the time, this quantity is not available in GaAs 2DEG, since it requires a backgate to vary the global electron density [45,46], which is a real challenge in high-mobility GaAs heterostructures.…”

Section: Thermoelectric Scanning Gate Microscopymentioning

confidence: 99%

Thermoelectric Scanning-Gate Interferometry on a Quantum Point Contact

et al. 2019

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We introduce a new scanning probe technique derived from scanning gate microscopy (SGM) in order to investigate thermoelectric transport in two-dimensional semiconductor devices. The thermoelectric scanning gate microscopy (TSGM) consists in measuring the thermoelectric voltage induced by a temperature difference across a device, while scanning a polarized tip that locally changes the potential landscape. We apply this technique to perform interferometry of the thermoelectric transport in a quantum point contact (QPC). We observe an interference pattern both in SGM and TSGM images, and evidence large differences between the two signals in the low density regime of the QPC. In particular, a large phase jump appears in the interference fringes recorded by TSGM, which is not visible in SGM. We discuss this difference of sensitivity using a microscopic model of the experiment, based on the contribution from a resonant level inside or close to the QPC. This work demonstrates that combining scanning gate microscopy with thermoelectric measurements offers new information as compared to SGM, and provides a direct access to the derivative of the device transmission with respect to energy, both in amplitude and in phase.

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“…The viscous regime has been widely investigated in graphene [2,3], where it is most pronounced at temperatures around 150 K. It was also shown in Ga[Al]As heterostructures using the Gurzhi effect [4] or Stockes flow [5], or based on a geometry which enables the measurement of the vicinity resistance [6]. In these experiments the temperature window was around 10 K. One hallmark of viscous flow that has been shown in graphene [7] but not yet in Ga [Al]As is the so-called superballistic flow through a point contact (PC) [8].…”

Section: Introductionmentioning

confidence: 99%

Structured back gates for high-mobility two-dimensional electron systems using oxygen ion implantation

Berl

Tiemann

Dietsche

et al. 2016

Applied Physics Letters

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We present a reliable method to obtain patterned back gates compatible with high mobility molecular beam epitaxy (MBE) via local oxygen ion implantation that suppresses the conductivity of an 80 nm thick silicon doped GaAs epilayer. Our technique was optimized to circumvent several constraints of other gating and implantation methods. The ion-implanted surface remains atomically flat which allows unperturbed epitaxial overgrowth. We demonstrate the practical application of this gating technique by using magneto-transport spectroscopy on a two-dimensional electron system (2DES) with a mobility exceeding 20 × 10 6 Vs/cm 2 . The back gate was spatially separated from the Ohmic contacts of the 2DES, thus minimizing the probability for electrical shorts or leakage and permitting simple contacting schemes. a) Electronic mail: mberl@phys.ethz.ch 1 arXiv:1601.01889v2 [cond-mat.mes-hall]

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Stable branched electron flow

Cited by 16 publications

References 21 publications

Energy stability of branching in the scanning gate response of two-dimensional electron gases with smooth disorder

Energy stability of branching in the scanning gate response of two-dimensional electron gases with smooth disorder

Thermoelectric Scanning-Gate Interferometry on a Quantum Point Contact

Structured back gates for high-mobility two-dimensional electron systems using oxygen ion implantation

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