flux vortex
/ fluks VOR-teks /
Stir a cup of coffee hard and a little whirlpool forms, a tidy spinning column with a quiet hole at its centre. Inside a type-II superconductor, magnetic field can punch through in exactly this whirlpool shape — a narrow swirling tube of current wrapped around a thin core that lets the field slip past, while the rest of the material stays untouched.
A flux vortex is such a microscopic tube threading a superconductor, and it carries one quantum of magnetic flux — a single fixed packet, never a fraction. At its heart is a tiny normal, non-superconducting core where the pairing is locally suppressed; around that core, a supercurrent circulates like the eddy around a drain, confining the field to that one slim channel. When many vortices crowd in, they repel one another and settle into a neat triangular grid, like logs floating in a regular pattern.
This matters because vortices are how strong-field superconductors survive at all, and managing them is the central engineering challenge in superconducting magnets and wires. The key misconception is to think the field somehow soaks through the whole material; in truth it is squeezed entirely into these isolated tubes, leaving everything between them perfectly superconducting. The catch is that if vortices are free to move, they bleed away energy, so they must be anchored to flaws in the crystal.
Using a special microscope, physicists can photograph the vortices in a type-II superconductor directly — they appear as a regular triangular lattice of bright dots, each dot one quantum of flux poking through the surface.
Flux vortices arrange into a regular triangular array, each carrying exactly one flux quantum.
The amount of flux in one vortex is set by a universal constant of nature involving the electron pair's charge, so every vortex in every type-II superconductor carries the very same tiny, fixed amount — direct evidence that the current is carried by pairs, not single electrons.