3 research outputs found
Phase Transitions in Isolated Vortex Chains
In very anisotropic layered superconductors (e.g. BiSrCaCuO)
a tilted magnetic field can penetrate as two co-existing lattices of vortices
parallel and perpendicular to the layers. At low out-of-plane fields the
perpendicular vortices form a set of isolated vortex chains, which have
recently been observed in detail with scanning Hall-probe measurements. We
present calculations that show a very delicate stability of this isolated-chain
state. As the vortex density increases along the chain there is a first-order
transition to a buckled chain, and then the chain will expel vortices in a
continuous transition to a composite-chain state. At low densities there is an
instability towards clustering, due to a long-range attraction between the
vortices on the chain, and at very low densities it becomes energetically
favorable to form a tilted chain, which may explain the sudden disappearance of
vortices along the chains seen in recent experiments.Comment: 9 pages, 10 figure
Particle transport in graphene nanoribbon driven by ultrashort pulses
We study charge transport in a graphene zigzag nanoribbon driven by an external
time-periodic kicking potential. Using the exact solution of the time-dependent Dirac
equation with a delta-kick potential acting in each period, we study the time evolution of
the population transfer probability and the time-dependent optical conductivity. By
variation of the kicking parameters, the conductivity becomes widely tunable