Stability of Branched Flow from a Quantum Point Contact

Liu, Bo; Heller, Eric J.

doi:10.1103/physrevlett.111.236804

Cited by 21 publications

(26 citation statements)

References 16 publications

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“…This is of practical importance because spin polarization should be very well reproducible in a large number of switching elements for spintronics circuits as indicated above. At the same time disorder of this type provides ideal models for fundamental studies of wave-chaotic transport [44].…”

Section: Introductionmentioning

confidence: 99%

Probing dopants in wide semiconductor quantum point contacts

Yakimenko¹,

Berggren²

2016

J. Phys.: Condens. Matter

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Effects of randomly distributed impurities on conductance, spin polarization and electron localization in realistic gated semiconductor quantum point contacts (QPCs) have been simulated numerically. To this end density functional theory in the local spin-density approximation has been used. In the case when the donor layer is embedded far from the two-dimensional electron gas (2DEG) the electrostatic confinement potential exhibits the conventional parabolic form, and thus the usual ballistic transport phenomena take place both in the devices with split gates alone and with an additional metallic gate on the top. In the opposite case, i.e. when the randomly distributed donors are placed not far away from the 2DEG layer, there are drastic changes like the localization of electrons in the vicinity of confinement potential minima which give rise to fluctuations in conductance and resonances. The conductance as a function of the voltage applied to the top gate for asymmetrically charged split gates has been calculated. In this case resonances in conductance caused by randomly distributed donors are shifted and decrease in amplitude while the anomalies caused by interaction effects remain unmodified. It has been also shown that for a wide QPC the polarization can appear in the form of stripes. The importance of partial ionization of the random donors and the possibility of short range order among the ionized donors are emphasized. The motivation for this work is to critically evaluate the nature of impurities and how to guide the design of high-mobility devices.

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Section: Introductionmentioning

confidence: 99%

Probing dopants in wide semiconductor quantum point contacts

Yakimenko¹,

Berggren²

2016

J. Phys.: Condens. Matter

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“…The interference of electron waves backscattered off the tip-depleted disc, off the QPC and impurities modulates the transmission probability of the latter and leads to the appearance of interference fringes along branches 2,3,18,22 . Scanning gate microscopy (SGM) studies have focused on completely open systems, such as quantum point contacts 2,3,[16][17][18][21][22][23][24][25][26][27][28][29] , and more closed systems, for example, cavities 19,[30][31][32][33][34][35] . In cavities irregular conductance fluctuations 19,[30][31][32] and regular fringes 19,35,36 originating from quantized tip-induced constrictions were observed.…”

Section: In Scanning Gatementioning

confidence: 99%

Electron backscattering in a cavity: Ballistic and coherent effects

et al. 2016

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Numerous experimental and theoretical studies have focused on low-dimensional systems locally perturbed by the biased tip of a scanning force microscope. In all cases either open or closed weakly gate-tunable nanostructures have been investigated, such as quantum point contacts, open or closed quantum dots, etc. We study the behaviour of the conductance of a quantum point contact with a gradually forming adjacent cavity in series under the influence of a scanning gate. Here, an initially open quantum point contact system gradually turns into a closed cavity system. We observe branches and interference fringes known from quantum point contacts coexisting with irregular conductance fluctuations. Unlike the branches, the fluctuations cover the entire area of the cavity. In contrast to previous studies, we observe and investigate branches under the influence of the confining stadium potential, which is gradually built up. We find that the branches exist only in the area surrounded by cavity top gates. As the stadium shrinks, regular fringes originate from tip-induced constrictions leading to quantized conduction. In addition, we observe arc-like areas reminiscent of classical electron trajectories in a chaotic cavity. We also argue that electrons emanating from the quantum point contact spread out like a fan leaving branch-like regions of enhanced backscattering.

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“…The electron wavelength in the experiment is 37nm, and the narrowest opening in the QPC is on the same order of magnitude. Semiclassically, one can imagine the effect of this QPC as aligning the initial momenta of the electrons in one direction while confining their positions down to nanoscales in the other direction [5]. This effectively creates an initial condition resembling that from a "point" injector.…”

Section: Discovery Of Branched Flowmentioning

confidence: 99%

Classical and Quantum Stability of Branched Flow

Liu

2015

J. Phys.: Conf. Ser.

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Abstract. Branched flow is a universal phenomenon of wave propagation in random media. From a classical point of view, branched flow is the overall pattern of classical electron trajectories moving in a potential with randomly placed weak scatterers. Individually, each electron trajectory is exponentially unstable to small perturbations due to the chaotic nature of the classical dynamics of electrons moving in a random potential. However, the overall pattern, branched flow, displays strong stability against large perturbations. In this paper, we discuss both the classical and quantum stability of branched flow against perturbations.

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Stability of Branched Flow from a Quantum Point Contact

Cited by 21 publications

References 16 publications

Probing dopants in wide semiconductor quantum point contacts

Probing dopants in wide semiconductor quantum point contacts

Electron backscattering in a cavity: Ballistic and coherent effects

Classical and Quantum Stability of Branched Flow

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