In superconductivity, a type-II superconductor is a superconductor that exhibits an intermediate phase of mixed ordinary and superconducting properties at intermediate temperature and fields above the superconducting phases.
It also features the formation of magnetic field vortices with an applied external magnetic field.
This occurs above a certain critical field strength Hc1. The vortex density increases with increasing field strength. At a higher critical field Hc2, superconductivity is destroyed. Type-II superconductors do not exhibit a complete Meissner effect.
Quantum vortices in a 200-nm-thick YBCO film imaged by scanning SQUID microscopy
Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered, even down to near absolute zero, a superconductor has a characteristic critical temperature below which the resistance drops abruptly to zero. An electric current through a loop of superconducting wire can persist indefinitely with no power source.
A high-temperature superconductor levitating above a magnet. Persistent electric current flows on the surface of the superconductor, acting to exclude the magnetic field of the magnet (Meissner effect). This current effectively forms an electromagnet that repels the magnet.
Top: Periodic table of superconducting elemental solids and their experimental critical temperature (T) Bottom: Periodic table of superconducting binary hydrides (0–300 GPa). Theoretical predictions indicated in blue and experimental results in red
Electric cables for accelerators at CERN. Both the massive and slim cables are rated for 12,500 A. Top: regular cables for LEP; bottom: superconductor-based cables for the LHC
Cross section of a preformed superconductor rod from the abandoned Texas Superconducting Super Collider (SSC)