Cuansing, Eduardo C. Jr
This research proposal is for the study of a quantum device we call a nanotransistor consisting of a source terminal, a central channel, and a drain terminal, attached together. Charged particles would flow from the source, through the channel, and then towards the drain. A gate then acts on the channel by applying an electric field, thereby modulating the charge and energy currents flowing through the device. Compared to the modern transistor, the nanotransistor has length scales of a few nanometers. The device therefore contains just several atoms and is constructed by directly manipulating molecules into place. Because of the small size of the device, quantum mechanics dominates the physics of the system. In addition, we allow the potential that the gate applies to the channel to vary in time therefore making the system go out of equilibrium. Incorporating quantum mechanics and nonequilibrium thermodynamics, the charge and energy currents can be calculated theoretically following an approach that uses nonequilibrium Green's functions techniques. These nonequilibrium Green's functions can be expressed in terms of integrals and then calculated using parallel numerical integration. Once data for the currents are obtained, relaxation, propagation, and response times can be determined by analyzing the currents at separate sites within the device. The nonequilibrium Green's functions approach is versatile enough in a way that the device can be made up of various materials such as an idealized linear chain of atoms, a long-chained molecular junction, a quasi-one-dimensional wire such as a carbon nanotube, or a two-dimensional sheet such as graphene. Results of the research can help us understand how nanodevices respond and behave under time-varying applied stimuli.