Condensed matter physics
Superconductivity and BCS theory
Explore the BCS model: Cooper pairs (two opposite-spin electrons) condense and open an energy gap in the excitation spectrum . Vary T/Tc and the pair density to watch close at the transition temperature.
Equipment
- Virtual crystal lattice with opposite-spin electron pairs
- Temperature slider T/Tc
- Pair-density slider and model parameter
- Excitation-spectrum plot $E(k)=\sqrt{\xi^2+\Delta^2}$ and readout $\Delta(T)/\Delta(0)$
Procedure
Observe Cooper pairs and the gap
Set T/Tc low (about 0.2): on the canvas, opposite-spin electron pairs appear stably, and the spectrum plot shows a forbidden region around the Fermi level — exciting a quasiparticle costs at least .
Raise temperature through the transition
Drag T/Tc from 0 up through 1: the readout falls to 0 at Tc, pairs break apart, and the spectral gap closes — the metal returns to its normal state. Record a few points (T/Tc, Δ/Δ(0)) to sketch the gap curve.
Change pair density and predict
Hold T/Tc fixed below 1 and lower the pair-density slider: fewer pairs mean a shallower gap in the model. Predict the spectrum as the density → 0 and verify it returns to the free parabola .