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 ($\Delta\cos(k_x)\cos(k_y)$) 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 ($\Delta[\cos(k_x)+\cos(k_y)]$) scenario no ABS at finite energy are found.Comment: 4 pages, 5 figure

O gênero Burkholderia: um importante componente da comunidade microbiana.

Descrição do gênero Burkholderia; Distribuição e diversidade; Patógenos em seres humanos e animais; Patógenos em plantas; Espécies diazotróficas em plantas não leguminosas; Espécies diazotróficas em plantas leguminosas; Promoção de crescimento em plantas; Controle biológico de doenças em plantas; Biorremediação.bitstream/CNPAB-2010/33991/1/doc219.pd

Uso de hipoclorito de sódio para acelerar a emergência das plântulas e desenvolvimento das mudas de cafeeiro.

Made available in DSpace on 2012-08-01T01:01:29Z (GMT). No. of bitstreams: 1 ArtigoBragantia.pdf: 91079 bytes, checksum: a5f5c324e664c0ea2e10dbd5a5e8a026 (MD5) Previous issue date: 2009-11-1

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

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