פרופ' בוריס שפירא - על מוליכות 86-858
א. מטרות הקורס:
Superconductivity is a fascinating and challenging field of physics. This importance is infinitely more than physics phenomena of the first order. It may be one of the fundamental linking mechanisms in an unlimited and connected universe. For nearly 75 years superconductivity has been a relatively obscure subject. Today however, superconductivity is being applied to many diverse areas such as: medicine, theoretical and experimental science, the military, transportation, power production, electronics, as well as many other areas. With the discovery of high-temperature superconductors, which can operate at liquid nitrogen temperatures (77 K), superconductivity is now gives unique and exciting opportunities to explore and experiment with this new and important technological field of physics.
ב. תוכן הקורס:
1. Basic Experiments.
Zero resistivity and the Meissner-Ochsenfeld effect. The magnetic flux quantization. Ultra-red absorption. Energy Gap. Isotopic effect. Knight Shift in NMR. Heat conductivity. AC properties. Type-I and Type-II superconductors. Magnetization curves. Critical current. Voltage-current characteristics.
2. Thermodynamic approach.
Free energy of a superconductor in magnetic field. Thermodynamic critical field. Heat capacity and entropy.
3. London approach.
Linear Electrodynamics. Pippard nonlocality. London equations. Magnetic field penetration depth. Gibbs energy and the first critical magnetic field. Vorticity. The Bean-Livingston surface barrier. Intervortex interaction, vortex lattice and the magnetization curves. Shear, compressive and tilt elastic modulus of the vortex lattice.
II. The Ginzburg-Landau Approach
1. The order parameter. Gauge invariance. Basic Equations. Boundary conditions. 1D solution. Two scales. Negative surface energy.
2. The second and third critical magnetic field. Abrikosov vortices. The vortex core and the magnetic penetration depth. Phase diagram.
3. Vortices in anisotropic superconductors. Second critical field. Vortex structure in 2D film. The Kosterlitz-Thauless effect. Phase diagram of a 2D superconductor. Lawrence-Doniach model. Pancakes and anisotropic vortices.
4. Type-III superconductors. Pinning centers and pinning force. Elasticity of the vortices. Critical domain. Collective pinning and vortex creep. The critical current and the Lorents force. The Bean critical state. AC conductivity.
The Josephson equations. The magnetic field effect and two-junction SQUID.
The extended Josephson contacts. Effect on applied RF Field. Shapiro steps.
III. Microscopic Approach
Electrons and glue bosons. The model BCS Hamiltonian. Bogoliubov transformation. Superconducting gap and the critical temperature. The diamagnetic current. Quasiparticles. Bogoliubov's self-consistent equations.
Andreev reflection. Quasiparticle tunneling. Microscopic theory of the Josephson effect. Normal and Anomalous Green function of the Fermi gas. Gor'kov-Nambu equations. Magnetic impurities in a superconductor. Microscopic derivation of the Ginzburg-Landau equations.
ג. חובות הקורס:
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