Overview

With the increasing miniaturisation of electronic circuits, the use of molecular structures as building blocks in such circuits has recently received increasing attention. An important first goal is to understand the electronic transport through a molecule placed between two electrodes. While, in general, real molecules require extensive quantum chemistry calculations, this project aims at revealing fundamental physical processes in the electron transport through molecules by means of simple model systems. This includes studies of the incoherent transport through molecules, of the potential profile across a molecule as well as of the charge transport under the influence of a high-frequency field.

Husimi functions are employed in this project to study localization transitions as well as entangled spin-½ states. As a positive definite phase-space distribution, the Husimi function allows to quantitatively describe how strongly a quantum state is localized in phase space. The inverse participation ratio is particularly well suited to perform a disorder average in the case of localization transitions in disordered systems. For entangled states, a relation with the length of the concurrence vector is found.

Die Funktionalität nanoskaliger Bauteile hängt entscheidend von den Transporteigenschaften über die Grenzflächen zwischen den verschiedenen Komponenten ab. Die elektronische Struktur der Komponenten im Volumen und am Kontakt sollen mit ab initio-Methoden wie der Dichtefunktionaltheorie (DFT) bestimmt werden. Die so gewonnenen Resultate werden dann mit quasiklassischen Methoden kombiniert, um eine realistische Beschreibung des elektronischen Transports, insbesondere für raue Grenzflächen sowie für endliche Spannungen, zu ermöglichen.