Single electron transport in parallel coupled quantum dot nanostructure.

摘要

This thesis presents an experimental study of low-temperature electron transport in parallel coupled double quantum dot systems. The devices are fabricated in GaAs/AlGaAs heterostructure material grown by molecular beam epitaxy and are patterned using electron-beam lithography. The quantum dots are defined in the two-dimensional electron gas in the heterostructure using independently adjustable electrostatic surface gates. The gate geometry allows control over both the interdot tunnel barrier and the potential barriers which confine the electrons to each quantum dot.; The device dimensions are sufficiently small that dramatic effects due to capacitive charging of the coupled dot system by a single electron can be observed in the conductance characteristics at dilution refrigerator temperatures. The experiments are designed to probe explicitly the role of quantum mechanical interdot coupling in the double dot device. As the tunnel-coupling between the two dots is increased, the effects of quantum charge fluctuations in the system are observed in the low-temperature conductance data. The emergence of a set of secondary peaks in the conductance data resulting from interdot charge fluctuations is explored, and data is presented on the evolution of these peaks with temperature and interdot conductance.