Environment-induced overheating phenomena in Au-nanowire based Josephson junctions.

Unlike conventional planar Josephson junctions, nanowire-based devices have a bridge geometry with a peculiar coupling to environment that can favor non-equilibrium electronic phenomena. Here we measure the influence of the electron bath overheating on critical current of several bridge-like junctions built on a single Au-nanowire. Using the Usadel theory and applying the two-fluid description for the normal and superconducting components of the flowing currents, we reveal and explain the mutual influence of the neighbouring junctions on their characteristics through various processes of the electron gas overheating. Our results provide additional ways to control nanowire-based superconducting devices.

Anomalous magneto-resistance of Ni-nanowire/Nb hybrid system.

We examine the influence of superconductivity on the magneto-transport properties of a ferromagnetic Ni nanowire connected to Nb electrodes. We show experimentally and confirm theoretically that the Nb/Ni interface plays an essential role in the electron transport through the device. Just below the superconducting transition, a strong inverse proximity effect from the nanowire suppresses superconducting correlations at Nb/Ni interfaces, resulting in a conventional anisotropic magneto-resistive response. At lower temperatures however, the Nb electrodes operate as superconducting shunts. As the result, the magneto-resistance exhibits a strongly growing hysteretic behavior accompanied by a series of saw-like jumps. The latter are associated with the penetration/escape of individual Abrikosov vortices that influence non-equilibrium processes at the Nb/Ni interface. These effects should be taken into account when designing superconducting quantum nano-hybrids involving ferromagnetic nanowires.

Dynamic properties of asymmetric double Josephson junction stack with quasiparticle imbalance.

We study analytically and numerically the influence of the quasiparticle charge imbalance on the dynamics of the asymmetric Josephson stack formed by two inequivalent junctions: the fast capacitive junction JJ 1 and slow non-capacitive junction JJ 2. We find, that the switching of the fast junction into resistive state leads to significant increase of the effective critical current of the slow junction. At the same time, the initial switching of the slow junction may either increase or decrease the effective critical current of the fast junction, depending on ratio of their resistances and the value of the capacitance. Finally, we have found that the slow quasiparticle relaxation (in comparison with Josephson times) leads to appearance of the additional hysteresis on current-voltage characteristics.

Ferromagnetic planar Josephson junction with transparent interfaces: a φ junction proposal.

We calculate the current-phase relation of a planar Josephson junction with a ferromagnetic weak link located on top of a thin normal metal film. Following experimental observations we assume transparent superconductor-ferromagnet interfaces. This provides the best interlayer coupling and a low suppression of the superconducting correlations penetrating from the superconducting electrodes into the ferromagnetic layer. We show that this Josephson junction is a promising candidate for experimental φ junction realization.