Topic summary
Physical state
Extracted from the Wikipedia article State of matter.
Superconductors and fermionic condensates
Superconductors are materials which have zero electrical resistivity, and therefore perfect conductivity. This is a distinct physical state which exists at low temperature, and the resistivity increases discontinuously to a finite value at a sharply defined transition temperature for each superconductor. A superconductor also excludes all magnetic fields from its interior, a phenomenon known as the Meissner effect or perfect diamagnetism. Superconducting magnets are used as electromagnets in magnetic resonance imaging machines.