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Vortex Dynamics in Type II Superconductors

Vortex Dynamics in Type II Superconductors. Yuri V. Artemov Ph.D. Student in Physics Mentor: Brian B. Schwartz Professor of Physics. CUNY Fall 1998. Overview. Properties of superconductors Two types of superconductors Theories of superconductivity Vortices in type II superconductors

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Vortex Dynamics in Type II Superconductors

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  1. Vortex Dynamics in Type II Superconductors Yuri V. ArtemovPh.D. Student in Physics Mentor:Brian B. SchwartzProfessor of Physics CUNY Fall 1998

  2. Overview • Properties of superconductors • Two types of superconductors • Theories of superconductivity • Vortices in type II superconductors • Interaction between vortices • Interaction with defects • Vortex dynamics • Proposed research • Vortices and computers • Summary

  3. Properties of Superconductors Perfect conductor Meissner effect Magnetic fielddestroys s/c Electric currentdestroys s/c Ic Bc 0

  4. Two Types of Superconductors Type I Type II -4M -4M H H Hc Hc1 Hc2 B B H H Hc Hc1 Hc2 Hc Hc Normal Metal Normal Metal Mixed State Superconductor T T Superconductor Tc Tc Magnetization Magnetic Field Critical Field

  5. Theories of Superconductivity H Superconductor Normal Metal 2 EF EF • London Equation • BCS Theory isotope effect • Electrons can attract via phonons • Attraction leads to energy gap 1.76Tc • Ginzburg-Landau Theory

  6. Vortices in Type II Superconductors H   r j   r  Order Parameter   r Magnetic Field Current

  7. Interaction between Vortices B J FL B B FL J Lorenz type force Repulsion Triangular lattice

  8. Interaction with Defects B J FL Flux Creep Activation energy behavior Pinning • Vacancies, voids, inhomogeneities, where superconductivity is weak • Pinning decreases energy losses caused by flux creep

  9. Vortex Dynamics • Collective behavior • Vortices interact strongly • Effects of disorder • Interaction with pinning centers • Many degrees of freedom • 1012 vortices in a sample • Threshold dynamics • Can be driven to marginally stable state

  10. Proposed Research Study the dynamics of vortices in type II superconductors • Given a superconductor with a certain pinning landscape, how do vortices move inside it? • How do microscopic pinning parameters affect measured macroscopic quantities? • How do vortices start moving when slowly driven towards the threshold of instability? • How to characterize dynamical instabilities in a superconductor?

  11. Vortices and Computers • Vortices can be studied using computer simulations • A powerful theoretical tool to answer questions raised above • Allows to study phenomena hard to observe experimentally • Vortices can be effectively visualized using modern 3D design software • Making them more understandable to non-physics audience • Tools to be used • Powerful workstations at the CUNY New Media Lab • Softimage 3D software • DirectX technology with Visual C++ and Visual Basic • Matlab, Mathematica • Java & WWW

  12. Summary • General properties of superconductors • Type I and type II superconductors • Theories of superconductivity • Vortices in type II superconductors • Vortex interactions and dynamics • Proposed research • Using computers to study and visualize vortices

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