Interactive visualization of the Meissner effect: superconductor magnetic levitation, flux expulsion, shielding currents, and flux pinning in type-II superconductors
Discovered by Walther Meissner and Robert Ochsenfeld in 1933, the Meissner effect is the expulsion of magnetic flux from a superconductor when cooled below its critical temperature Tc. Unlike a perfect conductor, a superconductor actively expels all internal magnetic fields — this is a thermodynamic phase transition, not just zero resistance. Inside a superconductor, B = 0 (in the Meissner state), and surface screening currents flow in a thin London penetration depth layer, generating an opposing field. This makes the superconductor a perfect diamagnet (χ = −1), enabling magnetic levitation.
The levitation force arises from the interaction between the permanent magnet's field and the superconductor's diamagnetic response. The image method gives a repulsive force as if a mirror dipole existed below the surface. The temperature-dependent order parameter Δ(T) ∝ (1 − (T/Tc)²)^(1/2) modulates screening current strength and penetration depth λ(T) = λ₀/√(1 − (T/Tc)⁴).
Type-II superconductors like YBCO have two critical fields Hc1 and Hc2. Between them, magnetic flux penetrates as quantized vortices (Φ₀ = h/2e ≈ 2.07×10⁻¹⁵ Wb). These vortices are pinned by crystal defects, creating quantum locking — the superconductor is locked in position and can levitate at any angle, even upside down.
Start with the YBCO preset. The main canvas shows magnetic field lines bending around the superconductor. Drag Temperature from 300K to 77K to see the phase transition — field lines are expelled as the material becomes superconducting. Increase Magnetic Field for stronger levitation. Adjust Flux Pinning to simulate type-II behavior: zero pinning allows free sliding, maximum pinning locks the superconductor in place. The T-B Phase Diagram shows the current operating point relative to critical curves.