7. Superconductivity - University of Liverpool

More documents

Recommendations

Info

Let us now see how this equation ∆φ = m ρq ∫ L J.dl + qΦ. can help us understand Meissner’s effect. For a simple lump of metal, the wavefunction would be continuous through the whole volume, so the phase change would be zero. The equation then simplifies to This means that: m ρq ∫ L J.dl = −qΦ. if there is a magnetic field in the macroscopic wavefunction, then is a there is an electric current. To see why this is special, consider Faraday’s law again. Superconductivity 21
Meissner effect. According to Faraday’s law, a change in magnetic flux is required before a current can be induced. For a macroscopic wavefunction, the very presence of the flux produces the current. No change in flux is needed! Let us look at the case of transition to the superconducting state again. Previously, we have not been able to explain the expulsion of the field using Faraday’s law. We can now explain this assuming that a macroscopic wavefunction appears when the metal becomes superconducting, If there is a magnetic field in the metal, it would produce a current. This current would in turn produce a flux. A more detailed reasoning would show that this wavefunction flux is in the opposite direction to the incoming flux. Superconductivity 22
Page 1 and 2: Statistical and Low Temperature Phy
Page 3 and 4: Resistance, magnetic field and heat
Page 5 and 6: Examples of superconductors. http:/
Page 7 and 8: Measuring magnetic field. This grap
Page 9 and 10: Heat capacity. Recall the heat capa
Page 11 and 12: If we select the normal conducting
Page 13 and 14: Explanation using macroscopic wavef
Page 15 and 16: Lenz’s law. According to Lenz’s
Page 17 and 18: Macroscopic wavefunction. We shall
Page 19 and 20: Ampere’s law. The right side of t
Page 21: ∫ ∆φ = m ∫L v.dl + q A.dl. L
Page 25 and 26: London’s penetration depth. Flux
Page 27 and 28: London penetration depth Assuming t
Page 29 and 30: Integrating the current along a cir
Page 31 and 32: Combining with the solenoid formula
Page 33 and 34: Vortices. In the lectures on superf
Page 35 and 36: Likewise, Essmann and Trauble sprin
Page 37 and 38: Type II superconductors. This shows
Page 39 and 40: Flux measurement. Deaver and Fairba
Page 41 and 42: In the case of the superfluid, no m
Page 43 and 44: So if we choose the loop L away fro
Page 45 and 46: Cooper pairs Superconductivity 44
Page 47 and 48: The Isotope Effect. If electrons re
Page 49 and 50: How electrons “attract” When a
Page 51 and 52: Cooper pair in real space The wavef
Page 53 and 54: Energy gap. As an example of a pred
Page 55 and 56: BCS superfluid. The most obvious pr
Page 57 and 58: Cooper pair The average charge in a
Page 59 and 60: When a lattice vibrates the maximum
Page 61 and 62: This is also the length, or extent,
Page 63 and 64: It has an energy 2E F − ∆, wher
Page 65 and 66: Applications of superconductors Sup
Page 67 and 68: Maglev train. A train can be levita
Page 69 and 70: Particle accelerators Particle acce
Page 71 and 72: High Temperature Superconductors In
Page 73:
Applications? Using these high temp
show all

7. Superconductivity - University of Liverpool

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?