246 research outputs found

    Propriedades térmicas e de barreira de filmes nanocompósitos à base de gelatina.

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    O desenvolvimento de materiais híbridos orgânicos/inorgânicos é uma alternativa a superar as limitações de desempenho dos materiais oriundos de polímeros naturais. No presente estudo, o efeito do teor de ZnO e a concentração de polietilenoglicol sobre a permeabilidade ao vapor de água e o perfil de decomposição térmica de filmes de gelatina foram analisados por meio de planejamento fatorial 2². Os resultados de PVA variaram entre 6,3x10-11 g.s-1.m-1.Pa-1 e 9,8-11 g.s-1.m-1.Pa-1. A incorporação de ZnO provocou uma redução da permeabilidade ao vapor de água dos filmes de gelatina e melhoria da estabilidade térmica. Os resultados opostos das propriedades foram observados para a incorporação do plastificante

    Ballistic Josephson junctions in edge-contacted graphene

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    Hybrid graphene-superconductor devices have attracted much attention since the early days of graphene research. So far, these studies have been limited to the case of diffusive transport through graphene with poorly defined and modest quality graphene-superconductor interfaces, usually combined with small critical magnetic fields of the superconducting electrodes. Here we report graphene based Josephson junctions with one-dimensional edge contacts of Molybdenum Rhenium. The contacts exhibit a well defined, transparent interface to the graphene, have a critical magnetic field of 8 Tesla at 4 Kelvin and the graphene has a high quality due to its encapsulation in hexagonal boron nitride. This allows us to study and exploit graphene Josephson junctions in a new regime, characterized by ballistic transport. We find that the critical current oscillates with the carrier density due to phase coherent interference of the electrons and holes that carry the supercurrent caused by the formation of a Fabry-P\'{e}rot cavity. Furthermore, relatively large supercurrents are observed over unprecedented long distances of up to 1.5 μ\mum. Finally, in the quantum Hall regime we observe broken symmetry states while the contacts remain superconducting. These achievements open up new avenues to exploit the Dirac nature of graphene in interaction with the superconducting state.Comment: Updated version after peer review. Includes supplementary material and ancillary file with source code for tight binding simulation
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