Quantum transport in open mesoscopic cavities

In this review we describe the results of magneto-transport studies in open quantum dots, in which electronic motion is expected to be predominantly ballistic in nature. The devices themselves are realized in different semiconductor materials, using quite distinct fabrication techniques. Electron interference is an important process in determining the electrical properties of the devices at low temperatures and is manifested through the observation of periodic magneto-conductance fluctuations. These are found to result from selective excitation of discrete cavity eigenstates by incoming electrons, which are directed into a collimated beam by the input point contact. Under conditions of such restricted injection, quantum mechanical simulations reveal highly characteristic wavefunction scarring, associated with the remnants of a few classical orbits. The scarring is built up by interference between electrons, confined within the cavities over very long time scales, suggesting the underlying orbits are highly stable in nature. This characteristic is also confirmed by the results of experiment, which reveal the discrete components dominating the interference to be insensitive to changes in lead opening or temperature. The fluctuations decay with increasing temperature, although they can nonetheless still be resolved at a few degrees kelvin. This characteristic is confirmed by independent studies of devices, fabricated using very different techniques, further demonstrating the universal nature of the behavior we discuss here. These results therefore demonstrate that the correct description of electron interference in open quantum cavities, is one in which only a few discrete orbits are excited by the collimating action of the input lead, giving rise to striking wavefunction scarring with measurable magneto-transport results.