Niobium's Mixed State

Plate 62 speaks for itself: “Single quanta.”

The Physics

In a type-II superconductor such as niobium, a magnetic field between B_c1 and B_c2 enters as vortices, each threading exactly one flux quantum, which settle into a hexagonal lattice.

B_c2 = Φ₀ / (2π ξ²)

• B_c2: upper critical field, T
• Φ₀: flux quantum h/2e ≈ 2.068×10⁻¹⁵ Wb
• ξ: coherence length, m

Each vortex carries Φ₀ = h/2e. Hexagonal lattice between B_c1 and B_c2.

Sources

• A. A. Abrikosov, Sov. Phys. JETP 5, 1174 (1957).
• U. Essmann, H. Träuble, Phys. Lett. A 24, 526 (1967).

On the poster

Plate 062, “Niobium's Mixed State”: the pixel-art plate with its slogan “Single quanta.”, the key equation and the facts panel shown above. Pixelated Physics. Physics. Personified.