Study Of Vortex Dynamics In Superconducting Thin Films Containing Defects

High-temperature superconducting materials are widely used in magnetic levitation,nuclear magnetic resonance,electrical transport and scientific equipment due to their remarkable ability to carry electric currents in a magnetic field.However,the extreme operating environment of superconductors requires them to be subjected to complex mechanical loads and deformations during operation.In addition,superconducting materials are inherently brittle materials,which are highly sensitive to mesoscopic defects due to their long-term operation in complex environments subject to electromagnetic fields and electromagnetic physical forces,often resulting in stress concentrations at the defects,leading to structural failure or even destruction,which directly affects the electromagnetic performance and structural reliability of superconducting materials.The study of the electromagnetic properties and mechanical response of high-temperature superconducting materials in magnetic fields is crucial to the problem of constraining the application of high-temperature superconducting magnets.In this dissertation,numerical simulations are used to study the vortex dynamics of high-temperature superconducting films under the action of a magnetic field.The effect of defects on the vortex dynamics of type Ⅱ superconducting films is analyzed,and the effect of pre-strain and different Ginzburg-Landau parameters κ on the internal magnetic flux of superconductors is investigated.First,the effect of mesoscopic defects on the vortex dynamics of type Ⅱ superconducting films considering pre-strain is investigated based on Ginzburg-Landau(GL)theory.The TimeDependent Ginzburg-Landau(TDGL)equation with strain is derived from the effective free energy of the superconductor and combined with the linear deformation theory,and its corresponding boundary conditions are obtained.Numerical simulations were performed using finite element software to investigate the different responses of vortex formation to tensile strain in superconductors in the presence of mesoscopic defects,to quantify the stabilized vortices,and to explore the trends of wave functions under different pre-strains.Subsequently,the change of energy inside the superconducting film during the vortex formation process is analyzed.Second,using the same research method,we investigated the vortex dynamics of superconducting thin films containing columnar defects.The TDGL equations were solved numerically using the partial differential equation solver module in the finite element software.In this process,we consider different Ginzburg-Landau parameters κ and defect density,analyze the scale of vortex formation under the influence of defect density,and discuss the number of vortex formation and the variation of the maximum value of the order parameter with the value of Ginzburg-Landau parameter κ.At the end,we analyze the variation of magnetization intensity with the value of κ.It has been shown that a certain number of defects will promote the movement of the magnetic flux inside the superconductor and facilitate the formation of vortices,and that the vortex movement and electromagnetic properties of the superconductor can be adjusted by controlling the defects.