Flux quantization

Flux quantization is a quantum phenomenon in which the magnetic field is quantized in the unit of $h/2e$, also known variously as flux quanta, fluxoids, vortices or fluxons.

Flux quantization occurs in Type II superconductors subjected to a magnetic field. Below a critical field H_c1, all magnetic flux is expulsed according to the Meissner effect and perfect diamagnetism is observed, exactly as in a Type I superconductor. Up to a second critical field value, H_c2, flux penetrates in discrete units while the bulk of the material remains superconducting. Both critical fields are temperature dependent, and tabulated values are the zero-temperature extrapolation unless otherwise noted.

See also

• Flux pinning
• Magnetic flux quantum

In 1961, two groups working independently discovered flux quantization - the fact that the magnetic flux through a superconducting ring is an integer multiple of a flux quantum.The Cooper pairs of a superconductor can tunnel through a thin insulating layer between two superconductors. This is the basis for the Josephson junction which is used in high-speed switching devices.<ref>http://hyperphysics.phy-astr.gsu.edu/hbase/solids/scqua.html/ref>