Loughborough University
Thesis-2010-Hassan.pdf (10.45 MB)

Electrodynamics of fluxon and semifluxon in 2D T-shaped Josephson Nano-Junctions

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posted on 2011-04-08, 08:54 authored by Hanaa S. Hassan
Dynamic properties of Josephson junctions are interesting due to the emission of high frequency radiation (up to THz range) from Josephson junctions, closely related to fluxon dynamics. A better understanding of this dynamics can help to improve the Josephson devices used for applications. Josephson junctions can also be of great use as T-shaped multiple Josephson junctions in Josephson electronic circuits. In general, T-junctions consist of two attached Josephson transmission lines: a main Josephson transmission line (MJTL) along the -axis, and an additional Josephson transmission line (AJTL) along the -axis. These junctions can use to create fluxons (solitons) in junctions without applied magnetic field, (called flux cloning phenomenon). This work is devoted to contributing to a clarification of the dynamic behaviour of solitons (fluxons) in 2D extended conventional T-shaped Josephson junctions (extended means an AJTL is larger than MJTL). A conventional T-junction is a MJTL along the x-axis which divides into two Josephson transmission lines along the x- and y-axes. In addition, we also attempt to elucidate further the concept of flux cloning in rotated T-junctions, which are 90 degrees anticlockwise rotation of conventional T-junction. In rotated Tjunction, a MJTL along the x-axis divide into two Josephson transmission lines along the y-axis. We find the first evidence of moving semifluxon and observe for the first time new phenomena of semifluxons and anti-semifluxons in both extended conventional and rotated T-junctions. We numerically study the electrodynamics behaviour of solitons in the standard Tshaped Josephson junction (conventional T-junction) in a magnetic field. Therefore, we describe theoretically how flux cloning circuits exist and give an opportunity for use as flux flow oscillators operating without applied magnetic field. The results that emerge give further support to the flux cloning mechanism.



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© H.S. Hassan

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A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.

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