Abstract
The influence of the incompressible strips on the integer quantized Hall effect (IQHE) is investigated, considering a cleaved-edge overgrown (CEO) sample as an experimentally realizable sharp edge system. We propose a set of experiments to clarify the distinction between the large-sample limit when bulk disorder defines the IQHE plateau width and the small-sample limit smaller than the disorder correlation length, when self-consistent edge electrostatics define the IQHE plateau width. The large-sample or bulk quantized Hall (QH) regime is described by the usual localization picture, whereas the small-sample or edge regime is discussed within the compressible/incompressible strips picture, known as the screening theory of QH edges. Utilizing the unusually sharp edge profiles of the CEO samples, a Hall bar design is proposed to manipulate the edge potential profile from smooth to extremely sharp. By making use of a side-gate perpendicular to the two-dimensional electron system, it is shown that the plateau widths can be changed or even eliminated altogether. Hence, the visibility of IQHE is strongly influenced when adjusting the edge potential profile and/or changing the dc current direction under high currents in the nonlinear transport regime. As a second investigation, we consider two different types of ohmic contacts, namely highly transmitting (ideal) and highly reflecting (non-ideal) contacts. We show that if the injection contacts are non-ideal, but still ohmic, it is possible to measure directly the non-quantized transport taking place at the bulk of the CEO samples. The results of the experiments we propose will clarify the influence of the edge potential profile and the quality of the contacts, under QH conditions.
Highlights
Standard to define a dimensionless parameter called the filling factor ν, which gives the ratio of the filling electron factor as density nel ν = nel/n to the density of magnetic flux
Exploiting the findings of the interaction theory of the integer quantized Hall effect (IQHE) [9] and local probe experiments [19], we claim that the longitudinal resistance evolves differently on sharp and smooth edges when transitioning between quantized Hall effect (QHE)
The explicit self-consistent calculations considering an asymmetric sample predict that the width of the magnetic field intervals in which IQHE is observed can be tuned by changing the current direction [16]
Summary
In standard molecular beam epitaxy (MBE), the crystal is grown in the z-direction layer by layer. As a first step a usual MBE growth process is performed; the crystal is removed from the chamber, thinned, scribed, returned to the chamber mounted at a 90◦ angle and cleaved in situ and regrown This process is known as the cleaved edge overgrowth (CEO) technique [27]. Of the quantum Hall systems via momentum-resolved tunneling experiments, utilizing the second 2DEG residing perpendicular to the Hall system [20, 21] These tunneling experiments show that the CEO edge provides an extreme sharp potential approximating an infinite wall. The Hall bar lies in the x yplane, obtained by usual MBE growth, whereas on the rhs of the crystal an additional AlGaAs layer is grown This is the CEO edge and is capped by a metallic gate. We briefly recall the complementary transport calculations utilized by the screening theory to elucidate IQHE
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