Dynamical Properties of Nanoscale Systems

University Of California-San Diego, La Jolla CA

Investigators

Abstract

TECHNICAL SUMMARY: This award supports theoretical research and education into dynamical properties of nanoscale systems. Researchers are investigating previously unexplored fundamental issues and novel phenomena concerning transport in nanoscale systems. Efforts are in developing novel approaches and theories to describe them, by combining first-principles methods and model calculations, and advancing predictions which can be tested with available experimental capabilities. Test bed systems for this research include (but are not limited to) atomic and molecular junctions, i.e., structures made of a relatively small number of atoms connected to much larger (bulk) electrodes. New research investigations are initiated in this work. Researchers will determine what the role of initial correlations and memory effects is on the transport properties of nanostructures. It is also intended to determine under which conditions the electron flow develops characteristics of a turbulent liquid. Researcher will theoretically investigate, for given a set of initial conditions, the spatial and temporal correlation laws of the electron dynamics in these systems. Practically, it is necessary to know how the above properties depend on i) the parameters of the electron liquid, such as its density and viscosity, ii) the resistance of the junction, and iii) its atomic geometry and structure. Finally, the grand question, is to determine whether a dynamical calculation of conductance, using time-dependent density-functional methods, is able to capture many-body effects, such as coulomb blockade, with available functionals. In this theoretical setting, the researcher plans to investigate novel many-body effects and concepts in spin transport. The first effect considered is related to the viscous nature of the electron liquid and gives rise to a dynamical spin resistance. The second one is due to the interaction between local resistivity spin dipoles, i.e., dipoles of local spin due to the scattering of electrons at the junction. These effects definitely contribute to magnetoresistance, and under certain conditions may even be the dominant contributions to spin transport in nanostructures. The above studies will be carried out using a combination of Time-Dependent Density-Functional Theory and analytical models. Predictions will be made which can be directly tested with available experimental capabilities. Beyond basic research, the investigations have practical and education consequences. There is a continuing effort to connect theoretical predictions with quantities that are verified experimentally. The effort contributes to the training of both graduate and undergraduate students as demonstrated by his past track record. All of the above projects are particularly suitable for a Ph.D. thesis. They involve a balanced combination of numerical and analytical work, as well a lot of novel physical concepts. This provides a robust educational experience for the advanced students studying for the doctorate. Selected aspects of the program are also amenable to undergraduate research giving the student studying science in college an opportunity to experience theoretical research and gain the associated experience and education. The research has practical implications in the operation of electrical circuits made of nanoscale systems. The physical insights obtained with this project will therefore generate basic knowledge and significant new input for future developments in the field. The integration of research and education within a challenging program like the present one will aid the preparation of highly skilled personnel with expertise in an area of high demand both in academia and in industry. NONTECHNICAL SUMMARY: This award supports theoretical research and education into dynamical properties of electrical conduction in nanoscale systems. Researchers are investigating previously unexplored fundamental issues and novel phenomena concerning transport in nanoscale systems. Efforts are in developing novel approaches and theories to describe them, by combining fundamental theoretical methods and model calculations, and advancing predictions which can be tested with available experimental capabilities. Test bed systems for this research include (but are not limited to) atomic and molecular junctions, i.e., structures made of a relatively small number of atoms connected to much larger (bulk) electrodes. Beyond basic research, the investigations have practical and education consequences. There is a continuing effort to connect theoretical predictions with quantities that are verified experimentally. The effort contributed to the training of both graduate and undergraduate students as demonstrated by his past track record. All of the above projects are particularly suitable for a Ph.D. thesis. They involve a balanced combination of numerical and analytical work, as well a lot of novel physical concepts this providing a robust educational experience for the advanced students studying for the doctorate. Selected aspects of the program are also amenable to undergraduate research giving the student studying science in college an opportunity to experience theoretical research and gain the associated experience and education. The research has practical implications in the operation of electrical circuits made of nanoscale systems. The physical insights obtained with this project will therefore generate basic knowledge and significant new input for future developments in the field. The integration of research and education within a challenging program like the present one will aid the preparation of highly skilled personnel with expertise in an area of high demand both in academia and in industry.