Nichtgleichgewichts-Ladungstransport in molekularen Nanostrukturen: Theorie und Anwendungen
Zusammenfassung der Projektergebnisse
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. The combined efforts of experimental investigations and theoretical modeling in recent years have provided a basic understanding of steady state quantum transport in molecular junctions. Important questions of current interest include transient and time-dependent phenomena as well as the theoretical description of molecular junctions with electron-electron and electron-vibrational interaction beyond minimal models. Within this context, the goal of the project was to develop theoretical methods that allow an accurate and efficient description of nonequilibrium transport processes, including transient dynamics, and apply these methods to elucidate and analyze fundamental physical mechanisms that determine charge transport in molecular junctions. To this end, two classes of approaches were considered: (i) methods based on the multilayer multiconfiguration timedependent Hartree methodology, which allows a very accurate, in principle numerically exact treatment of nonequilibrium transport, and (ii) quantum master equations, which due to their perturbative basis are limited to weak coupling and higher temperatures, but are less challenging to implement, in particular for more complex models. Based on the methodological advancement achieved within the project, several important aspects of nonequilibrium charge transport in molecular junctions were investigated. This includes the existence and uniqueness of steady states in molecular junctions, time scales and dynamics of approach to steady state as well transport and relaxation mechanisms related to electron-electron and electron-vibrational interaction. Furthermore, current fluctuations in molecular junctions with strong electronic-vibrational coupling were analyzed in detail. In addition, the possibility to control charge transport in molecular junctions using intramolecular proton transfer processes was investigated. It was shown that the current-voltage characteristics in systems with weak hydrogen bonds and a significant energy barrier for the proton transfer resemble those of a transistor or a diode. The results of this analysis demonstrate that field-controlled proton transfer is a promising mechanism to achieve functionality in molecular junctions.
Projektbezogene Publikationen (Auswahl)
- Sub-Ohmic to super-Ohmic crossover behavior in nonequilibrium quantum systems with electron-phonon interactions. Phys. Rev. B 92, 195143 (2015)
E.Y. Wilner, H. Wang, M. Thoss, and E. Rabani
(Siehe online unter https://doi.org/10.1103/PhysRevB.92.195143) - Employing an interaction picture to remove artificial correlations in multilayer multiconfiguration time-dependent Hartree simulations. J. Chem. Phys. 145, 164105 (2016)
H. Wang, and M. Thoss
(Siehe online unter https://doi.org/10.1063/1.4965712) - Vibrationally dependent electron-electron interactions in resonant electron transport through single-molecule junctions. Phys. Rev. B 93, 115421 (2016)
A. Erpenbeck, R. Hartle, M. Bockstedte, M. Thoss
(Siehe online unter https://doi.org/10.1103/PhysRevB.93.115421) - Controlling the conductance of molecular junctions using proton transfer reactions: A theoretical model study. J. Chem. Phys. 146, 092317 (2017)
C. Hofmeister, P.B. Coto, and M. Thoss
(Siehe online unter https://doi.org/10.1063/1.4974512) - A multilayer multiconfiguration time-dependent Hartree study of the nonequilibrium Anderson impurity model at zero temperature. Chem. Phys. 509, 13 (2018)
H. Wang and M. Thoss
(Siehe online unter https://doi.org/10.1016/j.chemphys.2018.03.021) - On the memory kernel and the reduced system propagator. J. Chem. Phys. 149, 104105 (2018)
L. Kidon, H. Wang, M. Thoss, and E. Rabani
(Siehe online unter https://doi.org/10.1063/1.5047446)
