Triangular lattice of flux tubes in a Type II superconductor, each carrying Φ₀ = h/2e
In Type II superconductors (κ = λ/ξ > 1/√2 ≈ 0.707), magnetic flux penetrates as quantized vortices, each carrying one flux quantum Φ₀ = h/2e ≈ 2.07×10⁻¹⁵ Wb. Abrikosov (Nobel 2003) showed these vortices arrange into a triangular (hexagonal) lattice to minimize energy. The lattice spacing a = (2Φ₀/√3·B)^(1/2) shrinks as field increases. Between Hc1 and Hc2 = Φ₀/(2πξ²), the vortex state coexists with superconductivity.