Scanning capacitance imaging of compressible quantum Hall effect stripes formed at the sample edge and at a potential fluctuation

Suddards, M.E.; Baumgärtner, A.; Mellor, C.J.; Henini, M.

doi:10.1016/j.physe.2007.09.172

Cited by 6 publications

(11 citation statements)

References 9 publications

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“…Figure 4(a) shows a composite image of numerous scans of Im(G ts,ω ) along ∼100 µm of the sample edge at ν = 1.90. In previous experiments, we found that the stripe width depends on the edge confinement potential [25]. Here we observe no significant variation in the shape or the amplitude of the stripes.…”

Section: Quantum Hall Effect (Qhe) Regimesupporting

confidence: 51%

“…These values are larger than those extracted from experiments on quantum point contacts [30,31], since the strip width scales inversely with the electron density gradient at the corresponding position [5]. Wider strips have been observed on tip-induced depleted regions of the 2DEG, with a more shallow density gradient [25]. In contrast to theoretical expectations [5], in our experiments the incompressible strips diverge into the bulk at non-integer bulk filling factors, consistent with the high-field end of the zero-resistance intervals of the longitudinal resistance.…”

Section: Interpretation and Discussionmentioning

confidence: 67%

“…In contrast, the magnitude of the imaginary part in figure 2(b) is significantly larger on the Hall bar than over the etched region. On the 2DEG the signal is homogeneous except for small variations introduced by the topography, as for example highlighted by arrows in figures 2(a) and (b) [25]. The physical edge does not correspond exactly to the onset of the capacitance signal, which we attribute to a depletion of the 2DEG near the edge due to missing dopants and the increased surface potential leading to the 2DEG confinement.…”

Section: Two-dimensional Electron Gas At Zero Fieldmentioning

confidence: 87%

“…This resolution is comparable to other scanning capacitance experiments with the tip in contact to the sample, but without the detrimental mechanical abrasion of the tip apex. Features in the DSCM images with a seemingly better lateral resolution can be traced back to changes in the average tip-sample distance due to topographic features on the surface, which are resolved with typical AFM resolution [25].…”

Section: Dynamic Scanning Capacitance Microscopymentioning

confidence: 99%

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Scanning capacitance imaging of compressible and incompressible quantum Hall effect edge strips

et al. 2012

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We use dynamic scanning capacitance microscopy to image compressible and incompressible strips at the edge of a Hall bar in a twodimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime. This method gives access to the complex local conductance, G ts , between a sharp metallic tip scanned across the sample surface and ground, comprising the complex sample conductance. Near integer filling factors we observe a bright stripe along the sample edge in the imaginary part of G ts . The simultaneously recorded real part exhibits a sharp peak at the boundary between the sample interior and the stripe observed in the imaginary part. The features are periodic in the inverse magnetic field and consistent with compressible and incompressible strips forming at the sample edge. For currents larger than the critical current of the QHE break-down the stripes vanish sharply and a homogeneous signal is recovered, similar to zero magnetic field. Our experiments directly illustrate the formation and a variety of properties of the conceptually important QHE edge states at the physical edge of a 2DEG.

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Section: Quantum Hall Effect (Qhe) Regimesupporting

confidence: 51%

Section: Interpretation and Discussionmentioning

confidence: 67%

Section: Two-dimensional Electron Gas At Zero Fieldmentioning

confidence: 87%

Section: Dynamic Scanning Capacitance Microscopymentioning

confidence: 99%

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Scanning capacitance imaging of compressible and incompressible quantum Hall effect edge strips

et al. 2012

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“…At integer filling factors, the 2DEG is insensitive to such a local gate, whereas at non-integer filling factors this technique can be used to gain information on the percolation transition of edge states and their mutual coupling. The compressible regions have been visualized by a scanning capacitance detection [17,18]. By additionally implementing a single electron transistor as local detector, both edge channels [19][20][21] as well as localized states [22] were resolved.…”

Section: Introductionmentioning

confidence: 99%

Optoelectronic transport through quantum Hall edge states

et al. 2015

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We use GaAs-based quantum point contacts as mesoscopic detectors to locally analyze the flow of photogenerated electrons in a two-dimensional electron gas (2DEG) at perpendicular, quantizing magnetic fields. The 2DEG is formed within a quantum well of a doped GaAs/AlGaAs-heterostructure. We find an optoelectronic signal along the lateral boundaries of the 2DEG, which is consistent with an optically induced quantum transport through quantum Hall edge channels. We demonstrate that photogenerated electrons can be directly injected into an edge channel, transported across several tens of micrometers and read-out on-chip by the quantum point contact.

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Low-temperature and high magnetic field dynamic scanning capacitance microscope

Baumgärtner

Suddards

Mellor

2009

Review of Scientific Instruments

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We demonstrate a dynamic scanning capacitance microscope (DSCM) that operates at large bandwidths, cryogenic temperatures, and high magnetic fields. The setup is based on a noncontact atomic force microscope (AFM) with a quartz tuning fork sensor for the nonoptical excitation and readout in topography, force, and dissipation measurements. The metallic AFM tip forms part of a rf resonator with a transmission characteristics modulated by the sample properties and the tip-sample capacitance. The tip motion gives rise to a modulation of the capacitance at the frequency of the AFM sensor and its harmonics, which can be recorded simultaneously with the AFM data. We use an intuitive model to describe and analyze the resonator transmission and show that for most experimental conditions it is proportional to the complex tip-sample conductance, which depends on both the tip-sample capacitance and the sample resistivity. We demonstrate the performance of the DSCM on metal disks buried under a polymer layer and we discuss images recorded on a two-dimensional electron gas in the quantum Hall effect regime, i.e. at cryogenic temperatures and in high magnetic fields, where we directly image the formation of compressible stripes at the physical edge of the sample.

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Scanning capacitance imaging of compressible quantum Hall effect stripes formed at the sample edge and at a potential fluctuation

Cited by 6 publications

References 9 publications

Scanning capacitance imaging of compressible and incompressible quantum Hall effect edge strips

Scanning capacitance imaging of compressible and incompressible quantum Hall effect edge strips

Optoelectronic transport through quantum Hall edge states

Low-temperature and high magnetic field dynamic scanning capacitance microscope

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