16 research outputs found
Inelastic electron transport in granular arrays
Transport properties of granular systems are governed by Coulomb blockade
effects caused by the discreteness of the electron charge. We show that, in the
limit of vanishing mean level spacing on the grains, the low-temperature
behavior of 1d and 2d arrays is insulating at any inter-grain coupling
(characterized by a dimensionless conductance g.) In 2d and g>>1, there is a
sharp Berezinskii-Kosterlitz-Thouless crossover to the conducting phase at a
certain temperature, T_{BKT}. These results are obtained by applying an
instanton analysis to map the conventional `phase' description of granular
arrays onto the dual `charge' representation.Comment: 24 pages, 8 figure
Electronic Transport in Hybrid Mesoscopic Structures: A Nonequilibrium Green Function Approach
We present a unified transport theory of hybrid structures, in which a
confined normal state () sample is sandwiched between two leads each of
which can be either a ferromagnet () or a superconductor () via tunnel
barriers. By introducing a four-dimensional Nambu-spinor space, a general
current formula is derived within the Keldysh nonequilibrium Green function
formalism, which can be applied to various kinds of hybrid mesoscopic systems
with strong correlations even in the nonequilibrium situation. Such a formula
is gauge invariant. We also demonstrate analytically for some quantities, such
as the difference between chemical potentials, superconductor order parameter
phases and ferromagnetic magnetization orientations, that only their relative
value appears explicitly in the current expression. When applied to specific
structures, the formula becomes of the Meir-Wingreen-type favoring strong
correlation effects, and reduces to the Landauer-B\"uttiker-type in
noninteracting systems such as the double-barrier resonant structures, which we
study in detail beyond the wide-band approximation.Comment: 24 pages, 12 eps figures, Revtex
Generalized uncorrelated SABR models with a high degree of symmetry
A family of generalized driftless uncorrelated SABR-like models are classified according to the dimensions of the symmetry groups of their corresponding backward Kolmogorov equations. This family contains the original uncorrelated SABR models, for arbitrary positive beta, as special cases. New cases with a rich symmetry group appear.Non-Gaussian option pricing, Derivative pricing models, Stochastic volatility, Partial differential equations,