Abstract
Quantum point contacts are fundamental building blocks for mesoscopic transport experiments and play an important role in recent interference and fractional quantum Hall experiments. However, it is unclear how electron–electron interactions and the random disorder potential influence the confinement potential and give rise to phenomena such as the mysterious 0.7 anomaly. Novel growth techniques of AlXGa1−XAs heterostructures for high-mobility two-dimensional electron gases enable us to investigate quantum point contacts with a strongly suppressed disorder potential. These clean quantum point contacts indeed show transport features that are obscured by disorder in standard samples. From these transport data, we are able to extract those parameters of the confinement potential that describe its shape in the longitudinal and transverse directions. Knowing the shape (and hence the slope) of the confinement potential might be crucial for predicting which interaction-induced states can best form in quantum point contacts.
Highlights
Quantum devices on semiconductor nanostructures rely on quantum point contacts (QPCs) as basic building blocks
Transport spectroscopy in the linear response regime demonstrates that conductance quantization is observed and that no scattering centers are found when shifting QPC1 between the gates
The 0.7-anomaly is investigated by varying the temperature and by applying a magnetic field perpendicular to the 2DEG
Summary
Quantum devices on semiconductor nanostructures rely on quantum point contacts (QPCs) as basic building blocks. Quantized conductance has been observed early on [1, 2] and it has been used as a signature of the quality of a QPC. With ever improving sample quality and the perspective for the detection of non-abelian anyons in the ν = 5/2 fractional quantum Hall state, several experiments [3, 4, 5] have recently used the properties of QPCs fabricated on ultra high-mobility two-dimensional electron gases (2DEGs). In view of proposals to investigate fractional quantum Hall states in confined geometries and interferometer-like setups, the detailed understanding and control of QPCs are essential. Higher order half plateaus are observed in the finite-bias differential conductance (at magnetic field B⊥ = 0 T) as well as spin-split half plateaus at B⊥ = 2 T. The 0.7-anomaly is investigated as a function of temperature and in perpendicular magnetic field
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