Experiment 9
Superconductivity Explorer: BCS Theory and the Meissner Effect
Visualize perfect diamagnetism and the temperature dependence of the superconducting energy gap.
Simulation Controls
Key Equations
BCS Energy Gap:
Δ(T) ≈ 1.74 Δ₀ √(1 - T/Tc)
London Equation:
B(x) = B₀ exp(-x/λL)
Meissner Effect: Flux Expulsion
Normal State
As T drops below Tc, magnetic field lines are expelled from the bulk (perfect diamagnetism).
BCS Gap vs Temperature
London Penetration Depth
Task: Meissner State
Start at T/Tc = 1.2. Slowly decrease the temperature. Notice how the magnetic field lines (grey) turn teal and bend aroundthe disk when T < Tc.
Teaching Connection
Superconductivity is the most dramatic demonstration in physics. A small piece of YBCO floating above a magnet is visually stunning and helps students grasp quantum phenomena.
Reflection Questions
- Why does the BCS energy gap close at the critical temperature Tc?
- What is the difference between a perfect conductor and a superconductor?
- Explain why liquid nitrogen (77 K) is used to cool YBCO but not Lead or Aluminium.