Non-equilibrium quantum effects in hybrid structures of ferromagnets and superconductors

Abstract

The quasiclassical theory of superconductivity is applied to diffusive nanowires connecting normal-metal and superconducting bulk materials. The diffusion equations for ferromagnetic junctions with spin-orbit coupling are generalized to include non-equilibrium phenomena. The main result of this thesis is an analytical method to calculate non-equilibrium quantities such as currents and differential electrical conductivity in systems with arbitrary spin structure at zero temperature. For more general systems that also include spin-orbit coupling, a numerical method is derived. It is shown that the rotation of the magnetization through the wire directly determines the long-range triplet density, reduces the Zeeman splitting of the zero-bias conductance peak in the differential conductivity spectrum. In systems with spin-orbit coupling it is found that both the triplet density and the position and height of peaks in the conductivity of the junction can be tuned by changing the relative orientation of the magnetization with respect to the wire.