Quantum point contacts

Quantum point contacts (QPCs) are a basic building block for many experiments in mesoscopic physics. Interference and tunneling experiments in the quantum Hall regime require detailed control and understanding of QPC confinement and transmission properties. A short review of the basic properties of QPCs is given. Optimized growth techniques allow the gating and study of QPCs on high-mobility two-dimensional electron gases, where the influence of disorder is strongly reduced. In these clean systems, the energy spectrum can be accessed via finite-bias transport, which allows us to characterize the shape of the confinement potential of the QPC. As the formation of compressible and incompressible stripes in the (fractional) quantum Hall regime depends sensitively on the steepness of the edge potential, understanding the confinement parameters is crucial for a further investigation of QPCs in finite magnetic fields.