Nonequilibrium Charge Transport in Molecular Nanostructures: Theory and Applications

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The study and understanding of quantum transport processes in molecular nanostructures has received great attention recently. Among the variety of processes and architectures investigated, charge and energy transport in molecular junctions, i.e. single molecules bound to metal or semiconductor electrodes, have been of particular interest. These systems combine the possibility to study fundamental aspects of nonequilibrium many-body quantum physics at the nanoscale with the perspective for technological applications in nanoelectronic devices. While a basic understanding of steady state transport properties in molecular junctions has been obtained, this is not the case for transient and time-dependent phenomena in these systems under nonequilibrium conditions. The objective of this proposal is to develop theoretical methods that allow an accurate and efficient description of nonequililbrium transport processes in molecular nanostructures and apply these methods to elucidate the fundamental physical mechanisms. Aspects to be investigated include the existence and uniqueness of steady states in molecular junctions, time scales and dynamics of approach to steady state, importance of relaxation mechanisms related to electron-electron and electron-vibrational interaction, switching and hysteresis, as well as possibilities to control pathways to specific quantum states under nonequilibrium conditions. Furthermore, fluctuation and noise phenomena will be investigated in the project. These aspects will be studied both for generic models as well as for specific examples of molecular junctions based on a first principles description. The long-term goal of this project is to obtain a comprehensive understanding of transient and time-dependent phenomena in transport processes in molecular nanostructures under nonequilibrium conditions.