Research review on electronic transport in quantum point contact (QPC) for quantum semiconductor devices applications

Quantum coherence effects play a prominent role in the electronic transport properties of mesoscopic systems. Up to now, most people have been concentrating on global transport properties by passing a current through the sample and measuring the voltage drop between leads connected to it. Doing so, the conductance of a narrow constriction in a 2-dimensional electron gas (2DEG), called a quantum point contact (QPC), was shown to be quantized in steps of the conductance quantum 2e ²/h as a function of its width. However, local information about transport through mesoscopic samples, e.g. in the form of a current density distribution, was experimentally unattainable for a long time. Only quite recently it became possible to probe the electron flow in a 2DEG locally with a STM. This review paper not emphasized to any result, but on to the concept of electron transport in QPCs for quantum devices and recent research in progress on it.