Superconductor

A material that, below a characteristic critical temperature and other limits, carries electrical current with zero resistance and expels magnetic fields through the Meissner effect.

Cooper pair: A bound pair of electrons that behaves collectively in a superconductor. Cooper pairs form the collective state that supports resistance-free current in conventional superconductors.
Electrical resistance: The opposition a material presents to the flow of electric current. Superconductors are distinguished by resistance falling to zero below their transition conditions.
Magnetic resonance imaging: A medical imaging technique that uses magnetic fields and radio waves to produce images of the body. Superconducting magnets provide the stable, intense fields used in many MRI scanners.
Type-I superconductor: A superconductor that expels magnetic fields completely until superconductivity abruptly breaks down at a critical field. Its single critical field contrasts with the mixed-state behavior of type-II materials.
High-pressure superconductivity: Superconductivity observed or sought in materials subjected to extreme pressure. Pressure can produce superconducting phases at elevated temperatures, but often only under impractical conditions.
BCS theory: A microscopic theory explaining conventional superconductivity through electron pairing mediated by lattice vibrations. It accounts for how paired electrons produce superconductivity in many elemental and alloy materials.
Magnetic flux: A measure of the magnetic field passing through a specified surface. The Meissner effect describes how superconductors expel magnetic flux from their interiors.
Magnetic levitation: The suspension of an object using magnetic forces without direct mechanical support. Flux expulsion and pinning can hold superconductors in stable levitation above magnets.
Type-II superconductor: A superconductor that admits magnetic flux vortices between lower and upper critical fields. Its broad magnetic-field range makes it suitable for high-field magnets.
Hydrogen-rich superconductors: Hydrogen-containing materials predicted or found to superconduct at high temperatures under pressure. They test predictions of strong conventional pairing while requiring extreme compression.

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