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High critical temperature superconductors (HTS) based devices can have impact in the study of the phase dynamics of Josephson junctions (JJs) thanks to the wide range of junction parameters they offer and to their unconventional properties. Measurements of current-voltage characteristics and of switching current distributions constitute a direct way to classify different regimes of the phase dynamics and of the transport, also in nontrivial case of the moderately damped regime (MDR). MDR is going to be more and more common in JJs with advances in nanopatterning superconductors and synthesizing novel hybrid systems. Distinctive signatures of macroscopic quantum tunneling and of thermal activation in presence of different tunable levels of dissipation have been detected in YBCO grain boundary JJs. Experimental data are supported by Monte Carlo simulations of the phase dynamics, in a wide range of temperatures and dissipation levels. This allows us to quantify dissipation in the MDR and partially reconstruct a phase diagram as guideline for a wide range of moderately damped systems. [ABSTRACT FROM AUTHOR]

Abstract: Self-assembled nanoscale channels may naturally arise in the growth process of grain boundaries (GBs) in high critical temperature superconductor (HTS) systems, and deeply influence the transport properties of the GB Josephson junctions (JJs). By isolating nano-channels in YBCO biepitaxial JJs and studying their properties, we sort out specific fingerprints of the mesoscopic nature of the contacts. The size of the channels combined to the characteristic properties of HTS favors a special regime of the proximity effect, where normal state coherence prevails on the superconducting coherence in the barrier region. Resistance oscillations from the current–voltage characteristic encode mesoscopic information on the junction and more specifically on the minigap induced in the barrier. Thouless energy emerges as a characteristic energy of these types of Josephson junctions. Possible implications on the understanding of coherent transport of quasiparticles in HTS and of the dissipation mechanisms are discussed, along with elements to take into account when designing HTS nanostructures. [Copyright &y& Elsevier]

Abstract: High quality YBa2Cu3O7−δ biepitaxial grain boundary junctions allowed one of the first evidences of macroscopic quantum behavior and mesoscopic transport in high critical temperature superconductors (HTS) systems. Both these studies touch delicate issues on fluctuations and give important feedback on the understanding of coherent transport of quasiparticles and of the dissipation mechanisms in HTS. [Copyright &y& Elsevier]

Abstract: We investigated transport properties of ultra-thin CaBaCuO (CBCO) films, focusing on vortex dynamics. By measuring current–voltage characteristics we found evidence that at high temperatures the vortices are thermally activated at the edges of the bridge and pushed in, causing dissipation and power-law dependence of the voltage from the current. At lower temperatures, the experimental curves change shape. We compared these data with the predicted behaviour for vortex quantum tunnelling and found a very good agreement. Measurements performed at ultra-low temperatures (down to 60mK) in a particular low noise environment provide additional evidence of the robustness of the observed effects. [Copyright &y& Elsevier]

Abstract: We report on transport measurements of Sr2RuO4–Sr3Ru2O7 eutectic crystals. In these systems, natural and clean interfaces are formed between the two phases thanks to the eutectic solidification process. The transport measurements, performed down to 300mK in a shielded environment, show a clear supercurrent flowing across the interface between Sr2RuO4 and Sr3Ru2O7, also when the contacts are placed at a distance of several hundreds of micrometers from the Sr2RuO4 domain. These results shed light on novel effects appearing in systems composed of the spin-triplet Sr2RuO4 and the metamagnet Sr3Ru2O7. [Copyright &y& Elsevier]

We have developed a fabrication process that allows us to realize pure YBCO nanowires displaying robust superconductivity at widths w as low as 160 nm. We can modify the process in order to maintain a Au protective layer. This allows us to scale our nanowires even further to widths as low as 50 nm. We have studied how the presence of vortices and the occurrence of phase slips affect the transport properties of nanowires in the width range ξ < w < λ , being ξ the coherence length and λ the magnetic penetration depth. Magnetoresistance curves present features which are related to the effect of screening currents. Vortex entry barrier is found to scale with the width. Our findings confirm that for widths ξ < w < λ nanowires are better protected against phase slips and vortex flow. [ABSTRACT FROM AUTHOR]

Abstract: Magneto-fluctuations of the normal resistance R N have been reproducibly observed in YBa2Cu3O7−δ (HTS) biepitaxial grain boundary junctions at low temperatures. We attribute them to mesoscopic transport in narrow channels across the grain boundary line. The Thouless energy appears to be the relevant energy scale. Possible implications on the understanding of coherent transport of quasiparticles in HTS and of the dissipation mechanisms are discussed. [Copyright &y& Elsevier]

Abstract: We describe the main ideas and some experimental outcomes of two experiments, both aimed to study quantum tunneling effects in high-T C structures. In the first experiment, macroscopic quantum tunneling is demonstrated in grain boundary YBaCuO Josephson junctions revealing dissipation levels lower than expected and opening novel perspectives for quantum circuitry. In the second, the low temperature dissipation is dominated by quantum tunneling of individual Pearl vortices in ultra-thin CaBaCuO systems characterized by extremely long Pearl lengths. [Copyright &y& Elsevier]