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 predo minantly ballistic in nature. The devices themselves are realized in d ifferent semiconductor materials, using quite distinct fabrication tec hniques. Electron interference is an important process in determining the electrical properties of the devices at low temperatures and is ma nifested through the observation of periodic magneto-conductance fluct uations. These are found to result from selective excitation of discre te 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 cha racteristic wavefunction scarring? associated with the remnants of a f ew classical orbits. The scarring is built up by interference between electrons, confined within the cavities over very long time scales, su ggesting the underlying orbits are highly stable in nature. This chara cteristic 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 wit h increasing temperature, although they can nonetheless still be resol ved at a few degrees kelvin. This characteristic is confirmed by indep endent 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 descriptio n of electron interference in open quantum cavities, is one in which o nly a few discrete orbits are excited by the collimating action of the input lead, giving rise to striking wavefunction scarring with measur able magneto-transport results. (C) 1997 Elsevier Science Ltd.