INTERNATIONAL PROFILE OF U.S. FOOD PROCESSORS

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Spin selective transport through helical molecular systems

Highly spin selective transport of electrons through a helically shaped electrostatic potential is demonstrated in the frame of a minimal model approach. The effect is significant even in the case of weak spin-orbit coupling. Two main factors determine the selectivity, an unconventional Rashba- like spin-orbit interaction, reflecting the helical symmetry of the system, and a weakly dispersive electronic band of the helical system. The weak electronic coupling, associated with the small dispersion, leads to a low mobility of the charges in the system and allows even weak spin-orbit interactions to be effective. The results are expected to be generic for chiral molecular systems displaying low spin-orbit coupling and low conductivity.Comment: 9 pages, 4 figures v2 (misprints corrected, new figures

Josephson Effect in Pb/I/NbSe2 Scanning Tunneling Microscope Junctions

We have developed a method for the reproducible fabrication of superconducting scanning tunneling microscope (STM) tips. We use these tips to form superconductor/insulator/superconductor tunnel junctions with the STM tip as one of the electrodes. We show that such junctions exhibit fluctuation dominated Josephson effects, and describe how the Josephson product IcRn can be inferred from the junctions' tunneling characteristics in this regime. This is first demonstrated for tunneling into Pb films, and then applied in studies of single crystals of NbSe2. We find that in NbSe2, IcRn is lower than expected, which could be attributed to the interplay between superconductivity and the coexisting charge density wave in this material.Comment: 3 pages, 2 figures. Presented at the New3SC-4 meeting, San Diego, Jan. 16-21 200

Collective effects in charge transfer within a hybrid organic-inorganic system

A collective electron transfer (ET) process was discovered by studying the current noise in a field effect transistor with light-sensitive gate formed by nanocrystals linked by organic molecules to its surface. Fluctuations in the ET through the organic linker are reflected in the fluctuations of the transistor conductivity. The current noise has an avalanche character. Critical exponents obtained from the noise power spectra, avalanche distributions, and the dependence of the average avalanche size on avalanche duration are consistent with each other. A plausible model is proposed for this phenomenonComment: 15 pages 4 figures. Accepted for publication in Physical Review Letter

Reactions of Oxygen Atoms with Van der Waals Complexes: The Effect of Complex Formation on the Internal Energy Distribution in the Products

Reactions of atomic oxygen with complexes containing HCl are investigated and the OH product state distributions are compared to those observed for the corresponding reactions of HCl monomers. In previous studies of reactions of O(3P) with HCl and hydrocarbon complexes, rotationally colder OH product state distributions were observed, when compared to the corresponding reactions of monomers. In contrast, we find that reactions of O(1D) with HCl clusters yield OH rotational distributions that are unaffected by the incorporation of HCl into a van der Waals complex. Quasiclassical trajectories are run on collisions of oxygen with HCl and Ar⋯HCl at 1 eV collision energies to investigate the differences in the dynamics of the O(1D) and O(3P) reactions. It is found that when the van der Waals complex is longer lived than the collision complex, rotational and vibrational cooling are observed. In contrast, when the dissociation of the van der Waals complex is prompt, compared to the collision complex lifetime, the effects of complex formation on the internal energy of the OH product become negligible

Universal transport in 2D granular superconductors

The transport properties of quench condensed granular superconductors are presented and analyzed. These systems exhibit transitions from insulating to superconducting behavior as a function of inter-grain spacing. Superconductivity is characterized by broad transitions in which the resistance drops exponentially with reducing temperature. The slope of the log R versus T curves turns out to be universaly dependent on the normal state film resistance for all measured granular systems. It does not depend on the material, critical temperature, geometry, or experimental set-up. We discuss possible physical scenarios to explain these findings.Comment: 4 pages, 3 figure

Chiral spintronics

As spins move through a chiral electric field, the resulting spin current can acquire chirality through a spin–orbit interaction. Such spin currents are highly useful in creating spin–orbit torques that can be used to manipulate chiral topological magnetic excitations, for example, chiral magnetic domain walls or skyrmions. When the chiral domain walls form composite domain walls, via an antiferromagnetic exchange coupling, novel phenomena, including an exchange coupling torque and domain wall drag, are observed. Here, we review recent progress in the generation and functionalities of spin currents derived from or acting on chiral structures. By bringing together advances in chiral molecules, chiral magnetic structures and chiral topological matter, we provide an outlook towards potential applications

Enhanced Electrochemical Water Splitting with Chiral Molecule-Coated Fe3O4 Nanoparticles

Photoelectrochemical (PEC) water splitting is a promising approach for generating hydrogen from water. In order to enhance PEC water splitting efficiency, it is essential to inhibit the production of the hydrogen peroxide byproduct and to reduce the overpotential required by an inexpensive catalyst and with high current density. In the past, it was shown that coating TiO2 electrodes by chiral molecules or chiral films enhances the hydrogen production and reduces the production of H2O2 byproduct. This was explained to be a result of the chiral-induced spin selectivity (CISS) effect that induces spin correlation between the electrons transferred to the anode. However, typically the current observed in those studies was in the range of 1-100 μA/cm2. Here we report currents in the range of 10 mA/cm2 obtained by adsorbing chiral molecules on a well-established Fe3O4 nanoparticle (NP) catalyst deposited on the anode. The results indicate a new strategy for designing low-cost earth-abundant catalysts where the advantages of the CISS effect are combined with the large effective area provided by the NPs to promote PEC water splitting with high current density