Periodic conductance fluctuations and lead-induced scarring in open quantum dots

Abstract

We consider the nature of ballistic electron transport in open mesoscopic cavities, coupled to external reservoirs by means of few-mode quantum point contacts. The devices vary in size over a wide range and the discrete nature of their electronic energy spectrum is expected to strongly influence the resulting electrical behaviour. Electron interference is also an important process in these devices and is investigated through studies of their low-temperature magneto-resistance. This is found to be characterized by regular fluctuations, which numerical simulations reveal to be associated with periodically recurring wavefunction scarring. Further analysis shows that the scarring is established by the collimating action of the injecting point contact, the quantum mechanical nature of which ensures that just a few cavity modes are excited to participate in transport. We therefore conclude that chaotic scattering is suppressed in mesoscopic cavities once their discrete quantum mechanical nature becomes resolved. Transport then instead occurs via a small number of regular orbits, which are stabilized by the role of the quantum point contact leads and the discrete quantization within the cavity itself. These long orbits give rise to well defined wavefunction scarring with measurable magneto-transport results.