Vortex matter in the two-band superconductor MgB2

L, CIVALE; A SERQUIS

MgB2 superconducting wires: Basics and applications

World Scientific

Año: 2016; p. 3 - 28

The physics of vortex matter in MgB2, the first discovered technologically relevant multiband superconductor, are determined by the parameters of the two gaps and by their coupling. The interplay of the quasi two-dimensional σ-band and the almost isotropic π-band results in anomalous and complex behavior of the characteristic lengths and critical fields. The coherence length and penetration depth are magnetic-field dependent, have different T dependence from those in single-band materials, and have different anisotropies. At low T and H the critical currents (Jc) are high and the relaxation rates (S) are low, indicative of large pinning energy. In clean MgB2, as H and T increase the  band contribution is strongly suppresed, so Jc decreases and S increases sharply, but C-doping allows maintaining strong pinning up to high fields as needed for applications.