7. Superconductivity - University of Liverpool

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Rearranging the relation gives this ratio: 2∆ k B T c = 3.52. The ratio for measured values are shown here: Meservey and Schwarz, in Parks (1969) Superconductivity The ratios are all fairly close to 3.52. This is another evidence that supports the BCS theory. Superconductivity 53
BCS superfluid. The most obvious property about a superconductor is the zero resistance. Unfortunately, there does not appear to be a simple way to explain this. The Cooper pairs can carry electric current, but why does it not get scattered by phonons and experience resistance? Victor Weisskopf suggested that the Cooper pairs are packed like atoms in the helium-4 superfluid, and has zero resistance for similar reasons. So the difficulty in scattering a Cooper pair is a result of interaction with other Cooper pairs. http://cdsweb.cern.ch/record/880131/files/p1.pdf The Cooper pairs would flow like a superfluid, unless there is enough energy to break all of them. This would happen at the transition temperature: k B T c ≈ ∆. Superconductivity 54
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 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: Energy gap. As an example of a pred
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
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7. Superconductivity - University of Liverpool

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