ConfiguraÃÃo, anisotropia e defeitos em uma rede de vÃrtices na presenÃa de nanoarmadilhas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Since Abrikosov s work in 1957, it. has been clear the vortex lattice existence and stability in specific magnetic fields and temperature values of type ll super- conductors. On external currents and Thermic fluctuations, vortices move through the superconductor salable resulting thermal dissipation. But it is salvage to most. actual technologic applications which are always trying to find electrical currents with the smallest resistivity. Thus, a possibility to avoid this dissipation is prevent vortex lines to move. One of the most practice and effective ways to stop vortex movement is in the superconductor sample introduce artificial pinning centers (idefects) . These defects are introduced by techniques of nanofabrication (for instance, nanolithographic techniques) producing random or regular pinning configurations. In the last case, arrays of pinning centers can induce vortex lattice configurations which critical currents is higher than critical currents in samples with random pinning centers. This fact is because the matching effect between vortex lattices and pinning arrays. In this way, to characterize these vortex phases depending on vortex density and symmetry of the pinning array is very important. to actual and future technologic applications. Moreover, the interaction between vortices and pinnings is a practice and simple model of interaction between an elastic lattice and a periodic substrate that can be used for many systems in condensed matter like colloids over periodic substrates or interference lasers, atoms adsorbed on a surface, vortices in Josephson junctions arrays and so on. In the present thesis, we study stable configurations, proliferation of defects and melting of vortex lattices, using Monde Carlo simulation, in two dimensional systems of thin superconductors films. Vortex lattice configurations has no trivial dependence on external magnetic field. These vortices are interacting with many different arrays of regular pinning centers: square lattices, rectangular lattices, line of isolated dots and so on. The melting phenomena was observed considering topological defects(dislocations,disclinations) role. The emergence of these topological defects depend directly on vortex lattice symmetry with pinning array and depend on the system temperature. Many vortex density were studied (magnetic field values). In special cases, we can found an anisotropic crystallization resulting an smectic phase. The smectic phase can be induced in some vortex density values and specific arrays of pinning centers

ASSUNTO(S)

fÃsica da matÃria condensada condensed matter physics superconductivity dinÃmica de vÃrtices supercondutividade fisica da materia condensada vortex dynamics

ACESSO AO ARTIGO

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