Magnetic flux quantum

Frozen current vortices (FCV) in superconductors can serve as essential elements of magnetic recording and as a convenient subject for investigations magnetic flux pinning at a transport current / across the superconductor, annihilation of two FCV with opposite magnetic flux, quantum behavior of frozen magnetic flux in the FCV, collective flow of FCV under the influence of the transport current I (Fig.5a). 

Here dm is the effective magnetic thickness of the junction, 0o the magnetic flux quantum, and My) the maximum Josephson current density. A complete oscillation of the pair current density is called a Josephson vortex and contains one magnetic flux quantum. This behavior is shown schematically in Fig. 5.10... 

Schilling et al. (1993) observed a cross-over in the irreversibility line measured with // II c on single-crystal specimens of a Bi2Sr2CaCu20g superconductor Irom a parabolic temperature dependence, //=/fo(l - T /T c). near to an exponential dependence, exp(const/7 ), at larger H and TIT < 0.5. They argued that the two regimes reflect a cross-over from essentially three-dimensional (3D) vortex fluctuations near Tc to quasi-two-dimensional (2D) vortex fluctuations for H >Ha ols y and low temperatures, where s is the interlayer distance, y=Ac/Aab is the anisotropy parameter, and 0o is the magnetic flux quantum. 

---