Investigations of electron wave interference and quantum chaos in ballistic quantum dots with square geometry

In this report we summarise the results of low temperature magneto-resistance studies, of electron transport in ballistic quantum dots. Evidence for the ballistic nature of motion in the dots is provided by the observation of: a clear linear form, to the weak localisation peak at very low magnetic fields, and; by the temperature dependent behaviour of the aperiodic fluctuations, observed over a much wider field range, which is found to be very different to that typical of disordered systems. The square geometry employed in the devices is of particular interest in studies of quantum chaos, since while the classical motion of particles in the geometry at zero field is known to be regular, theory predicts a transition to chaotic motion in a finite magnetic field, and in this report we also discuss the experimental evidence for this transition.