Glossary · Fundamentals
Abrikosov vortices carry magnetic flux through type II superconductors
An Abrikosov vortex is the structure through which magnetic flux enters a type II superconductor in its mixed state. Superconducting order is suppressed at the core, and currents circulate around it. A collection of vortices can form a lattice. [1]
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- DefinitionAbrikosov vortex
- A quantized magnetic-flux structure in a type II superconductor, with suppressed superconducting order at its core and circulating supercurrents around it. Interacting vortices can form an ordered vortex lattice in the mixed state.
Flux enters without destroying the entire superconducting state
Below the lower critical field, an ideal bulk type II superconductor has a Meissner state. Between its lower and upper critical fields, magnetic flux can enter as vortices. The surrounding material remains superconducting. At the upper critical field, bulk superconductivity is lost, so the mixed state occupies a bounded operating region. [1]
The vortex core is not a drilled hole or a separate foreign inclusion. It is a region where the superconducting order parameter is suppressed. Screening currents circulate around that region, and its magnetic field extends beyond the core. The existence of vortices therefore differs from ordinary field penetration through a uniformly normal metal. [1]
Flux quantization fixes the basic unit
University College London describes an elementary vortex carrying one magnetic flux quantum, given by Planck’s constant divided by twice the elementary charge [2]. Quantization follows from the coherent superconducting phase winding around the vortex. Increasing the mean field generally increases vortex density rather than continuously changing the elementary flux carried by each vortex. [1]
The field and superconducting order vary over different lengths. Coherence length sets the scale of the suppressed core, while penetration depth describes magnetic screening outside it. In a strongly type II material, the magnetic footprint can be much broader than the core. Both lengths are needed to describe the vortex structure. [1]
A vortex lattice is separate from the atomic lattice
Interacting vortices can arrange into a periodic pattern called an Abrikosov lattice. Abrikosov’s Nobel Lecture describes a triangular lattice as energetically favored in the isotropic model, while crystal symmetry can favor other arrangements. The vortex spacing changes with field. The pattern is a structure of the superconducting state rather than a new chemical crystal. [1]
Real samples contain defects, boundaries, and anisotropy that can distort or disorder this arrangement. Vortex imaging therefore probes both superconducting physics and the sample’s local structure. A regular theoretical lattice is a useful reference, but it should not be assumed to describe every region of a manufactured wire or coated tape. [1]
Pinning controls whether vortices dissipate energy
An applied transport current exerts a force on vortices. Their motion generates an electric field and dissipates energy, even while most of the material remains superconducting. Defects can restrain that motion through flux pinning. Useful current capacity in a magnetic field therefore depends on the vortex response as well as the existence of superconductivity. [3]
Pinning allows practical type II conductors to carry current, but changing fields and currents can still produce hysteresis losses. A magnet or cable specification should state temperature, field orientation, and transport-current conditions. Vortex structure explains the mixed state; measured pinning and loss behavior determine how that state performs in an engineered conductor. [3]
Sources
- Type II Superconductors and the Vortex LatticeNobel Prize, 2003
- Solid State Physics: Superconductivity II, A. H. HarkerUniversity College London
- Computation of losses in HTS under the action of varying magnetic fields and currents: University of Bath recordIEEE Transactions on Applied Superconductivity, 2014
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