Spectroscopy, Spin- and Charge Transport Properties of Andreev Molecule States

Electronic Transport through interfaces between ferromagnetic and non-magnetic metals constitutes the basis for functional structures in spintronics. Magnetic insulators are promising spin-valve materials for spintronic applications. In epitactic layered structures phase coherent transport becomes increasingly important with further miniaturization. A particularly clear experimental signature of spin-dependent phase-coherent transport is the occurrence of bound Andreev states due to nanoscale inhomogeneities of the interface between a ferromagnet and a superconductor, which will be investigated in the project. The possibility to guide super currents over large distances through ferromagnets is of fundamental importance as well as relevant for applications. This enables to taylor the quantum mechanical entanglement properties. To this end, we will compare the long-range proximity effect in different theoretical model systems with the experimentally fabricated structures and the measured transport properties.

Fig.1: Schematic view of Andreev bound states at spin-active interfaces.

Fig.2: The energy-dependent density of states D of the Andreev levels showing the spin splitting due to the interface parameter G^Φ (picture from P. Machon).