The transport through a metal-superconductor interface is governed by a special charge conversion process, the Andreev reflection, where each incident electron drags another electron with itself to form a Cooper pair. At the normal side a hole is lef
t behind dressed by superconducting correlations. For a low transparency interface the simultaneous transfer of two charges is strongly suppressed leading to a reduced conductance. Here we demonstrate that this reduced conductance can be turned to an infinite one by tuning the nanoscale geometry. Creating variable size nanojunctions between a thin metallic film and a superconducting tip we study how multiple phase-coherent scatterings enhance the superconducting correlations at the normal side. By increasing the coherent volume of carriers initially the transmission through the interface is continuously enhanced. However, as the phase-coherent volume reaches the opposite surface of the thin film a resonator is formed, and a robust transition is induced due to Cooper pair condensation.
High magnetic field study of Hall resistivity in the ferromagnetic phase of (In,Mn)Sb allows one to separate its normal and anomalous components. We show that the anomalous Hall term is not proportional to the magnetization, and that it even changes
sign as a function of magnetic field. We also show that the application of pressure modifies the scattering process, but does not influence the Hall effect. These observations suggest that the anomalous Hall effect in (In,Mn)Sb is an intrinsic property and support the application of the Berry phase theory for (III,Mn)V semiconductors. We propose a phenomenological description of the anomalous Hall conductivity, based on a field-dependent relative shift of the heavy- and light-hole valence bands and the split-off band.
