We study the vortex configuration in a superconducting macroscopic flat disk with central defects in the presence of a uniform applied magnetic field. Owing to the defects nature on the thin disk, vortices are able to form geometry induced, quasi-symmetric configurations of disk, triangle and concentric shells in the rest of the disk. The theoretical study made on this mesoscopic systems allows us to trace not only how the vortex pattern evolves with magnetic field, but also how the defect can be used to show the pinning and anti-pinning effect. The magnetic induction, vortex number, magnetization and Cooper pairs density as a function of the external magnetic field are calculated, we show that in our sample novels vortex configurations are possible due to the size of the disk and if the hole or barrier defect is considered.
The binding energy of bilayer spherical quantum dots (BSQDs) with randomly distributed neutral donor [Formula: see text] is computationally simulated. We analyze the ground state energy by using different potentials of confinement that include changes in its height, transition region and width, considering theoretical development in which the variational procedure takes a trial function as a product of the ground state wavefunction of the uncoupled electron in the heterostructure, with a correlation function that depends only on electron–ion separation. We find that the curves of the binding energy with repulsive layer have additional peaks, whose position and height depend on the configuration of the confinement is chosen at the center of the dot. Additionally, our results include novel curves for the density of [Formula: see text] impurity states for different potentials’ shapes.
It is well-known that the time dependent Ginzburg-Landau theory is a reliable theoretical tool to investigate the Shubnikov state in a superconductor sample in presence of an external applied magnetic field. In this work, we solved the system of the Ginzburg-Landau equations in two and three dimensions for two particular cases: For a parallelepiped with volume V p ; with transversal area S p = 9ξ 2 (0), 36ξ 2 (0) and height h p = 1ξ (0), 6ξ (0), where ξ (0) is the coherence length. In the other hand, for a thin disk with a centered circular and triangular defect, with topology of dot/anti-dot. In both cases are immersed into a homogeneous magnetic field. The effects of pinning/anti-pinning forces due to defects in the disk and demagnetization effects due to the finite size of the parallelepiped on configuring vortices and critical fields are discussed. In the tridimensional case, the magnetic field and the order parameter are not invariant along the direction z.Key words: Ginzburg-Landau, Mesoscopic System, Vortices. ResumenEs bien conocido que la teoría de Ginzburg-Landau es una herramienta teórica confiable para investigar el estado de Shubnikov en muestras superconductoras en presencia de campos magnéticos aplicados. En este trabajo resolvemos el sistema de ecuaciones Ginzburg Landau en dos y tres dimensiones en dos casos particulares: para un paralelepípedo de volumen V p ; con área transversal S p = 9ξ 2 (0), 36ξ 2 (0) y altura h p = 1ξ (0), 6ξ (0), donde ξ (0) es la longitud de coherencia y por otra parte, para un disco fino con un defecto circular y triangular centrado con topología punto/anti-punto. En ambos casos las muestran estan submersas en un campo magnético homogeneo. Los efectos de las fuerzas de anclaje/anti-anclaje debido a los defectos en el disco y los efectos de demagnetización debido al tamaño finito del paralelepipedo sobre la configuración de vortices y campos críticos son discutidos. En el caso tridimensional, el campo magnético y el parámetro de orden no son invariantes a lo largo de la dirección z.
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