Superconductors as ideal spin sources for spintronics

Spin-polarized transport is investigated in normal metal-superconductor (NS) junctions as a function of interface transmissivity as well as temperature when the density of states of a superconductor is Zeeman-split in response to an exchange field (h_exc). Similarly to the "absolute spin-valve effect" predicted by D. Huertas-Hernando et al. [Phys. Rev. Lett. 88, 047003 (2002)] in superconducting proximity structures, we show that NS junctions can be used to generate highly spin-polarized currents, in alternative to half-metallic ferromagnets. In particular, the spin-polarized current obtained is largely tunable in magnitude and sign by acting on bias voltage and h_exc. While for tunnel contacts the current polarization can be as high as 100%, for transparent junctions it is dominated by the minority spin species. The effect can be enhanced by electron "cooling" provided by the superconducting gap.Comment: 4 pages, 4 color figures, published versio

Bioerosion on a Terebratula scillae population from the Lower Pleistocene of Lecce area (Southern Italy)

This paper deals with shell bioerosion in a population of Terebratula scillae SEGUENZA from the Lower Pleistocene in Lecce area, Southern Italy. The most important traces belong to shell breakage attributed to predatory activity; borings (Entobia isp., Maeandropolydora isp.); drill holes (Oichnus simplex BROMLEY; Oichnus isp.); and etching scars (Centrichnus eccentricus BROMLEY and MARTINELL; Podichnus centrifugalis BROMLEY and SURLYK).The distribution analysis of the traces of epibiosis on the shells of T. scillae induces us to think that we are dealing with a pedicleanchored form, living with completely raised valves. Besides, both percentage and nature of predation marks (probably due to gastropods or decapod crustaceans) do not depose for a very intense predation pressure

Bioerosion on a Terebratula scillae population from the Lower Pleistocene of Lecce area (Southern Italy)

This paper deals with shell bioerosion in a population of Terebratula scillae SEGUENZA from the Lower Pleistocene in Lecce area, Southern Italy. The most important traces belong to shell breakage attributed to predatory activity; borings (Entobia isp., Maeandropolydora isp.); drill holes (Oichnus simplex BROMLEY; Oichnus isp.); and etching scars (Centrichnus eccentricus BROMLEY and MARTINELL; Podichnus centrifugalis BROMLEY and SURLYK). The distribution analysis of the traces of epibiosis on the shells of T. scillae induces us to think that we are dealing with a pedicle-anchored form, living with completely raised valves. Besides, both percentage and nature of predation marks (probably due to gastropods or decapod crustaceans) do not depose for a very intense predation pressure.El presente artículo trata sobre la bioerosión en las conchas de una población de Terebratula scillae SEGUENZA del Pleistoceno inferior del área de Lecce, Sur de Italia. Las principales trazas pertenecen a roturas de la concha atribuidas a la actividad de depredadores; perforaciones (Entobia isp., Maeandropolydora isp.); agujeros (Oichnus simplex BROMLEY; Oichnus isp.); e impresiones (Centrichnus eccentricus BROMLEY and MARTINELL; Podichnus centrifugalis BROMLEY and SURLYK). El análisis de la distribución de las trazas de epibiosis sobre las conchas de T. scillae induce a pensar que se trata de una forma anclada mediante el pedículo, que vivía con las valvas completamente levantadas. Por otra parte, ni los porcentajes ni la naturaleza de las señales de depredación (probablemente debidas a gasterópodos o a crustáceos decápodos) indican una presión de depredación demasiado intensa

Local density of states in metal - topological superconductor hybrid systems

We study by means of the recursive Green's function technique the local density-of-states of (finite and semi-infinite) multi-band spin-orbit coupled semiconducting nanowires in proximity to an s-wave superconductor and attached to normal-metal electrodes. When the nanowire is coupled to a normal electrode, the zero-energy peak, corresponding to the Majorana state in the topological phase, broadens with increasing transmission between the wire and the leads, eventually disappearing for ideal interfaces. Interestingly, for a finite transmission a peak is present also in the normal electrode, even though it has a smaller amplitude and broadens more rapidly with the strength of the coupling. Unpaired Majorana states can survive close to a topological phase transition even when the number of open channels (defined in the absence of superconductivity) is even. We finally study the Andreev-bound-state spectrum in superconductor-normal metal-superconductor junctions and find that in multi-band nanowires the distinction between topologically trivial and non-trivial systems based on the number of zero-energy crossings is preserved.Comment: 11 pages, 12 figures, published versio

Characterizing electron entanglement in multiterminal mesoscopic conductors

We show that current correlations at the exit ports of a beam splitter can be used to detect electronic entanglement for a fairly general input state. This includes the situation where electron pairs can enter the beam splitter from the same port or be separated due to backscattering. The proposed scheme allows to discriminate between occupation-number and degree-of-freedom entanglement.Comment: 5 pages, 1 figure. Ref. adde

Phase-Dependent Electronic Specific Heat in Mesoscopic Josephson Junctions

We study the influence of superconducting correlations on the electronic specific heat in a diffusive superconductor-normal metal-superconductor Josephson junction. We present a description of this system in the framework of the diffusive-limit Green's function theory, taking into account finite temperatures, phase difference as well as junction parameters. We find that proximity effect may lead to a substantial deviation of the specific heat as compared to that in the normal state, and that it can be largely tuned in magnitude by changing the phase difference between the superconductors. A measurement setup to confirm these predictions is also suggested.Comment: 4+ pages, 4 figure

Electronic implementations of Interaction-Free Measurements

Three different implementations of interaction-free measurements (IFMs) in solid-state nanodevices are discussed. The first one is based on a series of concatenated Mach-Zehnder interferometers, in analogy to optical-IFM setups. The second one consists of a single interferometer and concatenation is achieved in the time domain making use of a quantized electron emitter. The third implementation consists of an asymmetric Aharonov-Bohm ring. For all three cases we show that the presence of a dephasing source acting on one arm of the interferometer can be detected without degrading the coherence of the measured current. Electronic implementations of IFMs in nanoelectronics may play a fundamental role as very accurate and noninvasive measuring schemes for quantum devices.Comment: 12 pages, 10 figure