ON THE ROLE OF CLASSICAL ORBITS IN MESOSCOPIC ELECTRONIC SYSTEMS

We discuss the semiclassical periodic orbit theory (POT) and some of i ts recent extensions which are applicable also to systems exhibiting a transition from integrable to chaotic behaviour. We apply the POT to give a semiclassical interpretation of shell effects in free metal clu sters and semiconductor quantum dots in terms of classical periodic or bits. In particular, we study the ground-state deformations of large m etal clusters and discuss the recently observed conductance oscillatio ns in a circular quantum dot under the influence of an external magnet ic field. We also predict the shell structure of a triangular quantum dot, using as models a triangular billiard and the Henon-Heiles potent ial including weak magnetic fields.