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 junctions 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[1] and underdamped SIFS-type.[2]