10 research outputs found
Weak localisation in bilayer graphene
We have performed the first experimental investigation of quantum
interference corrections to the conductivity of a bilayer graphene structure. A
negative magnetoresistance - a signature of weak localisation - is observed at
different carrier densities, including the electro-neutrality region. It is
very different, however, from the weak localisation in conventional
two-dimensional systems. We show that it is controlled not only by the
dephasing time, but also by different elastic processes that break the
effective time-reversal symmetry and provide invervalley scattering.Comment: 4 pages, 4 figures (to be published in PRL
A dual point description of mesoscopic superconductors
We present an analysis of the magnetic response of a mesoscopic
superconductor, i.e. a system of sizes comparable to the coherence length and
to the London penetration depth. Our approach is based on special properties of
the two dimensional Ginzburg-Landau equations, satisfied at the dual point
Closed expressions for the free energy and the
magnetization of the superconductor are derived. A perturbative analysis in the
vicinity of the dual point allows us to take into account vortex interactions,
using a new scaling result for the free energy. In order to characterize the
vortex/current interactions, we study vortex configurations that are out of
thermodynamical equilibrium. Our predictions agree with the results of recent
experiments performed on mesoscopic aluminium disks.Comment: revtex, 20 pages, 9 figure
Surface superconducting states and paramagnetism in mesoscopic superconductors
In the framework of the Ginzburg-Landau equation, the temperature dependence
of the upper critical field of small ring-like superconductors is studied. At
equilibrium small parts of the phase diagram show paramagnetism for width /
radius ratios below 0.85. Their number and extension increase with the size of
the hole. In these regions, only the inner part of the ring shows a positive
magnetic moment. The order parameter density profile appears to change, when
crossing a first order transition line, which separates different angular
momentum values, and we clarify the relationship between the localization of
superconductivity nucleation and paramagnetism of those samples.Comment: 11 pages, 9 figure
Interaction phenomena in graphene seen through quantum capacitance
Contains fulltext :
111525.pdf (preprint version ) (Open Access