The role of lead openings in regular mesoscopic billiards

We discuss the results of experimental studies of ballistic electron transport in regular (i.e. non-chaotic) quantum dots. At low temperatures, coherent interference between electrons gives rise to reproducible fluctuations in the magneto-resistance, as well as to a weak localization peak near zero field. The lineshape of the peak evolves from a Lorentzian to a linear form, as the leads of the dot are closed, while the fluctuations exhibit striking quasiperiodicity, suggesting that transport through regular dots is dominated by just a small group of trajectories. Simulations show that these characteristics in turn result from the ability of the quantum point contact leads, to strongly select which trajectories participate in transport. (C) 1996 Academic Press Limited