3,648 research outputs found
Theory of Andreev reflection in a two-orbital model of iron-pnictide superconductors
A recently developed theory for the problem of Andreev reflection between a
normal metal (N) and a multiband superconductor (MBS) assumes that the incident
wave from the normal metal is coherently transmitted through several bands
inside the superconductor. Such splitting of the probability amplitude into
several channels is the analogue of a quantum waveguide. Thus, the appropriate
matching conditions for the wave function at the N/MBS interface are derived
from an extension of quantum waveguide theory. Interference effects between the
transmitted waves inside the superconductor manifest themselves in the
conductance. We provide results for a FeAs superconductor, in the framework of
a recently proposed effective two-band model and two recently proposed gap
symmetries: in the sign-reversed s-wave () scenario
resonant transmission through surface Andreev bound states (ABS) at nonzero
energy is found as well as destructive interference effects that produce zeros
in the conductance; in the extended s-wave ()
scenario no ABS at finite energy are found.Comment: 4 pages, 5 figure
Screening effects in flow through rough channels
A surprising similarity is found between the distribution of hydrodynamic
stress on the wall of an irregular channel and the distribution of flux from a
purely Laplacian field on the same geometry. This finding is a direct outcome
from numerical simulations of the Navier-Stokes equations for flow at low
Reynolds numbers in two-dimensional channels with rough walls presenting either
deterministic or random self-similar geometries. For high Reynolds numbers,
when inertial effects become relevant, the distribution of wall stresses on
deterministic and random fractal rough channels becomes substantially dependent
on the microscopic details of the walls geometry. In addition, we find that,
while the permeability of the random channel follows the usual decrease with
Reynolds, our results indicate an unexpected permeability increase for the
deterministic case, i.e., ``the rougher the better''. We show that this complex
behavior is closely related with the presence and relative intensity of
recirculation zones in the reentrant regions of the rough channel.Comment: 4 pages, 5 figure
A Comparative Evaluation of Two Distributed Hydro-Sedimentological Models in The Semiarid Region of the State of Paraíba, Brazil
Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv
Transmission of correlated electrons through sharp domain walls in magnetic nanowires: a renormalization group approach
The transmission of correlated electrons through a domain wall in a
ferromagnetic one dimensional system is studied theoretically in the limit of a
domain wall width smaller or comparable to the electron Fermi wavelength. The
domain wall gives rise to both potential and spin dependent scattering of the
charge carriers. Using a poor man's renormalization group approach for the
electron-electron interactions, we obtain the low temperature behavior of the
reflection and transmission coefficients. The results show that the
low-temperature conductance is governed by the electron correlations, which may
suppress charge transport without suppressing spin current. The results may
account for a huge magnetoresistance associated with a domain wall in ballistic
nanocontacs.Comment: 13 pages, 6 figure
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