Condensed-Matter Physics & Materials Science Seminar

The Josephson effect is still a unique key towards a variety of frontier problems ranging from the detection of Majorana fermions to macroscopic quantum phenomena and qubit applications. Progress in material science in producing a larger variety of interfaces and in nanotechnologies applied to superconductivity, may promote a renewal on the paradigms of the phase dynamics of Josephson junctions with relevant consequences on a series of key issues. We will discuss some relevant experiments mostly realized on unconventional junctions, including hybrid devices, nano-junctions, and especially high critical temperature superconductors (HTS). Novel phenomena emerge because of the possibility of driving materials and junctions with an accurate control in unexplored regimes. We have investigated different micro-structural configurations, which offer a wide range of junction dynamical parameters. A transition from classical Josephson phase dynamics, which takes place in junctions characterized by low values of critical current density Jc, to a regime in which dissipation is driven by local heating processes, for high values of Jc. We demonstrate how non-equilibrium effects and local processes in constrained geometry are codified in the response of the junctions and can be disentangled from other effects. Escape dynamics turns as an active 'imaging' of nano-scale transport with an enormous potential and the ability of encoding subtle transport information in fluctuations. We speculate on possible intrinsic nanoscale ordering occurring in HTS systems. This transition is of relevance for all kinds of weak links including the emergent family of nano-hybrid junctions. Information on the search of quantum phase slips can be also derived. Experiments on reference systems as HTS nanowires and Josephson junctions with ferromagnetic spin-valve tunnel barriers (experiment made in collaboration with University of Cambridge) will be finally