Doctoral Thesis: Nichtgleichgewichts-Green-Funktionen zur Beschreibung mesoskopischer Systeme (German)

The aim of this work is the theoretical description of electronic structures as well as transport properties of planar tunnel junctions, nanocontacts and scanning-tunneling-like geometries under bias voltage. Based on the fundamentals of the density functional theory we use a combination of the Keldysh formalism with the multiple scattering method named after Korringa, Kohn and Rostoker (KKR). The resulting implementation includes a self-consistent treatment of both charge relaxation and changes in the potential landscape induced by the bias voltage. Furthermore, the usage of the Keldysh formalism allows for an improved determination of conductance and current. By means of our procedure it is possible to treat planar tunnel junctions as well as nanocontacts on the same footing. In particular, we avoid any supercell effects in the description of the latter. We demonstrate our method exemplarily for different parallel plate capacitors and nanocontacts.

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Diploma Thesis: Electronic Transport Through Magnetic Nanocontacts

Ab initio calculations of the electronic structure and transport properties of magnetic nanocontacts consisting of cobalt (Co) and nickel (Ni) are presented.

The electronic structure of the nanocontacts was calculated self-consistently in the framework of the density functional theory by using the Korringa-Kohn-Rostoker multiple scattering Greens function method. The transport properties in the linear response regime were described by means of the Landauer approach in the formulation of Baranger and Stone.

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