Ginzburg-Landau parameter

The Ginzburg-Landau parameter, often denoted as κ (kappa), is a value used in the physics of superconductors to distinguish between different types. It compares two characteristic lengths: the penetration depth (how far magnetic fields can enter a superconductor) and the coherence length (the size of regions where electrons pair up). If κ is less than about 1/√2, the superconductor is called "type I," which expels magnetic fields completely. If κ is larger, it's "type II," allowing magnetic fields to penetrate in quantized vortices. This parameter helps scientists understand and predict superconducting behavior under magnetic fields.