Superconductivity

A state in which a material has zero electrical resistance and expels magnetic fields below a critical temperature, field, and current. Its macroscopic behavior arises from a quantum-coherent state of charge carriers.

Cooper pair: A bound pair of electrons formed in a superconductor through an effective attraction, often mediated by lattice vibrations. Cooper pairing underlies conventional superconductivity and enables a coherent superconducting state.
Electrical resistance: The opposition a material presents to electric current, converting some electrical energy into heat. Superconductivity is defined in part by resistance falling exactly to zero.
Type I superconductor: A superconductor that expels magnetic fields until superconductivity abruptly ends at one critical field. It shows the simplest form of magnetic flux exclusion, unlike mixed-state materials.
Superconducting magnet: An electromagnet whose windings use superconducting wire to carry large currents with negligible resistive loss. Zero-resistance current enables the strong, persistent fields used in MRI and research facilities.
Heike Kamerlingh Onnes: A Dutch physicist who discovered superconductivity in mercury in 1911 while studying materials at low temperatures. His low-temperature measurements first revealed the abrupt disappearance of electrical resistance.
BCS theory: A microscopic theory explaining conventional superconductivity through Cooper pairing and a macroscopic quantum state. It accounts for how electron pairing produces zero resistance and an energy gap.
Quantum coherence: The preservation of definite phase relationships among components of a quantum system. Long-range coherence lets many paired carriers behave as one superconducting state.
Type II superconductor: A superconductor that admits magnetic flux in quantized vortices between two critical fields. Its vortex state permits superconductivity to persist under stronger magnetic fields.
Magnetic resonance imaging: A medical imaging technique that uses strong magnetic fields and radio waves to produce images inside the body. Many MRI scanners rely on superconducting magnets for stable, powerful fields.
Mercury: A chemical element with symbol Hg that is liquid near room temperature and becomes superconducting at very low temperature. Mercury was the material in which superconductivity was first observed.

Linked from 64 pages