Anomalous transport in normal-superconducting and ferromagnetic-superconducting nanostructures

We have calculated the temperature dependence of the conductance variation [δS(T)] of mesoscopic superconductor–normal-metal (S/N) structures, in the diffusive regime, analyzing both weak and strong proximity effects. We show that in the case of a weak proximity effect there are two peaks in the dependence of δS(T) on temperature. One of them (known from previous studies) corresponds to a temperature T1 of order of the Thouless energy (εTh), and another, newly predicted maximum, occurs at a temperature T2 where the energy gap in the superconductor Δ(T2) is of order εTh. In the limit Lφ<L the temperature T1 is determined by Dħ/L2φ(Lφ is the phase breaking length), and not εTh. We have also calculated the voltage dependence δS(V) for a S/F structure (F is a ferromagnet) and predict nonmonotonic behavior at voltages of order the Zeeman splitting.