7. Superconductivity - University of Liverpool

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Flux quantisation. We have seen that vortices of electrons do exist in a superconductor. Lets now look at whether they are quantised. If the current around a vortex is quantised, so is the magnetic flux produced. This can be measured, the has indeed been found to be quantised. Deaver and Fairbank, Physical Review Letters, vol. 7 (1961) p. 43 Superconductivity 37
Flux measurement. Deaver and Fairbank measured the flux through a long, thin tube made of Tin: 1. Apply a magnetic field to the tube. 2. Cool below the 3.7 K transition temperature. 3. Move the tube up and down rapidly. 4. Place a coil near the end of the tube. 5. Measure the voltage induced in the coil. 6. Obtain the flux from the voltage. Superconductivity 38
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 and 22: ∫ ∆φ = m ∫L v.dl + q A.dl. L
Page 23 and 24: Meissner effect. According to Farad
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: Type II superconductors. This shows
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

7. Superconductivity - University of Liverpool

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