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Vortex Dynamics in Magnetic Phase Diagram of High Tc Cuprate Oxides

Taherian Fard, Hossein | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46850 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Khosroabadi, Hossein; Akhavan, Mohammad
  7. Abstract:
  8. In the 1950s, Abrikosov predicted the mixed state in superconductors (type II superconductors) which lead to a Noble Prize in 2003 with the experimental verification by shubnikov. Mixed-state is a network of magnetic flux lines with quantized flux (vortices) in superconductors. High-temperature superconductors are of Type II which the existense of vortices in a significant part of the temperature-field phase diagram of them, is an obvious phenomenon. These superconductors provided a proper context for understanding physical phenomena related to vortices and access to experimental data to compare with those provided by statistical mechanics. Vortices can move inside the superconductor by the influence of various factors such as interaction with each other, the Lorentz force due to the electric current, thermal fluctuations, quantum fluctuations and other factors which leads to resistance and electrical dissipation of energy.This factor limits the amount of current that can flow in superconductors without loss of energy. The vortex pinning by crystalline disorder or defects which increases the critical current density, is of great importance in applications of superconductivity. These factors also cause different phases of the Abrikosov network such as vortex liquid, vortex glass and other phases. In this thesis the causes of creation of vortices and the properties of them such as magnetic field and the supercurrent around them in homogenius and anisotropic superconductors and the amound of flux that each vortex carry, is studied. The equilibrium and dynamic phases of them in high-temperature superconductors is also investigated. The general features of the software vdsim (Vortex Dynamics SIMulation) are listed and the vortex state with a variety of pinning potential and transport current is simulated with it. Vortex density threshold for the formation of the hexagonal lattice is obtained. Critical current density for several pinning potentials is compared and the rate of changes with different parameters is studied and finally the temprature dependence of the critical current density is investigated
  9. Keywords:
  10. High Temperature Superconductor ; VORTEX ; Phase Diagram ; Mixed State

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