Newly synthesized nanostructures of graphene appear as a promising breeding ground for new technology. Therefore, it is important to identify the role played by boundary conditions in their electronic features. In this contribution we use non-equilibrium Green's function method coupled tight-binding theory calculate and compare current patterns hexagonal quantum dots, with contacts placed at di...

Experiments in the early 1980s have shown that a compact bundle of quantum vortex rings superfluid helium remains coherent and travels significant distance compared to its size. This is surprising because single ring, under effect friction with background thermal excitations (the so-called normal fluid), would quickly lose energy decay. The observation these long-lived structures has remained a...

We investigate the phenomenon of the diffraction of charged particles by thin material targets using the method of the de Broglie-Bohm quantum trajectories. The particle wave function can be modeled as a sum of two terms ψ = ψingoing + ψoutgoing. A thin separator exists between the domains of prevalence of the ingoing and outgoing wavefunction terms. The structure of the quantum-mechanical curr...

Josephson-junction arrays are ideal model systems to study a variety of phenomena such as phase transitions, frustration effects, vortex dynamics and chaos. In this review, we focus on the quantum dynamical properties of lowcapacitance Josephson-junction arrays. The two characteristic energy scales in these systems are the Josephson energy, associated with the tunneling of Cooper pairs between ...

Using results from sheaf theory combined with the phenomenological theory of the two-dimensional superfluid, the precipitation of quantum vortices is shown to be the genesis of a macroscopic order parameter for a phase transition in two dimensions.