physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...

, a fluxon is a

quantum In physics, a quantum (: quanta) is the minimum amount of any physical entity (physical property) involved in an interaction. The fundamental notion that a property can be "quantized" is referred to as "the hypothesis of quantization". This me ...

of electromagnetic flux. The term may have any of several related meanings.

Superconductivity

In the context of

superconductivity Superconductivity is a set of physical properties observed in superconductors: materials where Electrical resistance and conductance, electrical resistance vanishes and Magnetic field, magnetic fields are expelled from the material. Unlike an ord ...

, in type II superconductors fluxons (also known as Abrikosov vortices) can form when the applied field lies between

B_

and

B_

. The fluxon is a small whisker of normal phase surrounded by superconducting phase, and

Supercurrent A supercurrent is a superconducting current, that is, electric current which flows without dissipation in a superconductor. Under certain conditions, an electric current can also flow without dissipation in microscopically small non-superconductin ...

s circulate around the normal core. The magnetic field through such a whisker and its neighborhood, which has size of the order of London penetration depth

\lambda_L

(~100 nm), is quantized because of the phase properties of the

magnetic vector potential In classical electromagnetism, magnetic vector potential (often denoted A) is the vector quantity defined so that its curl is equal to the magnetic field, B: \nabla \times \mathbf = \mathbf. Together with the electric potential ''φ'', the ma ...

quantum electrodynamics In particle physics, quantum electrodynamics (QED) is the Theory of relativity, relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quant ...

, see

magnetic flux quantum The magnetic flux, represented by the symbol , threading some contour or loop is defined as the magnetic field multiplied by the loop area , i.e. . Both and can be arbitrary, meaning that the flux can be as well but increments of flux can be ...

for details. In the context of long Superconductor-Insulator-Superconductor Josephson tunnel junctions, a fluxon (aka

Josephson vortex In superconductivity, a Josephson vortex (after Brian David Josephson, Brian Josephson from Cambridge University) is a quantum vortex of supercurrents in a long Josephson junction, Josephson junction (see Josephson effect). The supercurrents circu ...

) is made of circulating

supercurrent A supercurrent is a superconducting current, that is, electric current which flows without dissipation in a superconductor. Under certain conditions, an electric current can also flow without dissipation in microscopically small non-superconductin ...

s and has ''no'' normal core in the tunneling barrier. Supercurrents circulate just around the mathematical center of a fluxon, which is situated with the (insulating) Josephson barrier. Again, the magnetic flux created by circulating

s is equal to a

\Phi_0

(or less, if the superconducting electrodes of the Josephson junction are thinner than

\lambda_L

Magnetohydrodynamics modeling

In the context of numerical MHD modeling, a fluxon is a discretized magnetic field line, representing a finite amount of magnetic flux in a localized bundle in the model. Fluxon models are explicitly designed to preserve the

topology Topology (from the Greek language, Greek words , and ) is the branch of mathematics concerned with the properties of a Mathematical object, geometric object that are preserved under Continuous function, continuous Deformation theory, deformat ...

of the magnetic field, overcoming

numerical resistivity Numerical may refer to: * Number * Numerical digit * Numerical analysis Numerical analysis is the study of algorithms that use numerical approximation (as opposed to symbolic computation, symbolic manipulations) for the problems of mathematical ...

effects in Eulerian models.

References

External links

FLUX
a fluxon-based MHD simulator Theoretical physics Superconductivity Josephson effect {{theoretical-physics-stub