Semifluxon
Encyclopedia
In superconductivity
, a Semifluxon is a vortex
of supercurrent
carrying the magnetic flux
equal to the half of the magnetic flux quantum
. Semifluxons exist in the so-called 0-π long Josephson junction
s at the boundary between 0 and π regions. For a shorter junction length (approx. Josephson penetration depth
λJ) the vortex does not fit into the junction and the flux inside the junction is reduced.
For the first time semifluxons were observed using d-wave superconductors at so called tricrystal grain boundaries and later in YBa2Cu3O7–Nb ramp zigzags. In these systems the phase shift of π takes place inside the d-wave superconductor
and not at the barrier. Due to the advent of controlled coupling by proper chosen ferromagnetic thicknesses,
0–π JJs have also recently been realized in low-Tc SFS-like systems
and underdamped SIFS-type.
Superconductivity
Superconductivity is a phenomenon of exactly zero electrical resistance occurring in certain materials below a characteristic temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum...
, a Semifluxon is a vortex
Vortex
A vortex is a spinning, often turbulent,flow of fluid. Any spiral motion with closed streamlines is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex...
of supercurrent
Supercurrent
A supercurrent is a superconducting current, that is, electric current which flows without dissipation....
carrying the magnetic flux
Magnetic flux
Magnetic flux , is a measure of the amount of magnetic B field passing through a given surface . The SI unit of magnetic flux is the weber...
equal to the half of the magnetic flux quantum
Magnetic flux quantum
The magnetic flux quantum Φ0 is the quantum of magnetic flux passing through a superconductor. The phenomenon of flux quantization was discovered B. S. Deaver and W. M. Fairbank and, independently, by R. Doll and M. Nabauer, in 1961...
. Semifluxons exist in the so-called 0-π long Josephson junction
Long Josephson junction
In superconductivity, a long Josephson junction is a Josephson junction which has one or more dimensions longer than the Josephson penetration depth \lambda_J. This definition is not strict....
s at the boundary between 0 and π regions. For a shorter junction length (approx. Josephson penetration depth
Josephson penetration depth
In superconductivity, Josephson penetration depth characterizes the typical length on which an externally-applied magnetic field penetrates into the long Josephson junction...
λJ) the vortex does not fit into the junction and the flux inside the junction is reduced.
For the first time semifluxons were observed using d-wave superconductors at so called tricrystal grain boundaries and later in YBa2Cu3O7–Nb ramp zigzags. In these systems the phase shift of π takes place inside the d-wave superconductor
and not at the barrier. Due to the advent of controlled coupling by proper chosen ferromagnetic thicknesses,
0–π JJs have also recently been realized in low-Tc SFS-like systems
and underdamped SIFS-type.