Proximity effect (superconductivity)

of the superconductor is suppressed and signs of weak superconductivity are observed in the normal material over mesoscopic distances.

Conversely, the (gapless) electron order present in the normal metal is also carried over to the superconductor in that the superconducting gap is lowered near the interface.

The microscopic model describing this behavior in terms of single electron processes is called Andreev reflection.

in a spin-singlet superconductor is largest when the normal material is ferromagnetic, as the presence of the internal magnetic field weakens superconductivity (Cooper pairs breaking).

The study of S/N, S/I and S/S' (S' is lower superconductor) bilayers and multilayers has been a particularly active area of superconducting proximity effect research.

Similar qualitative changes in behavior do not occur when a magnetic field is applied perpendicular to the S/I or S/N interface.

In S/N and S/I multilayers at low temperatures, the long penetration depths and coherence lengths of the Cooper pairs will allow the S layers to maintain a mutual, three-dimensional quantum state.

As temperature is increased, communication between the S layers is destroyed resulting in a crossover to two-dimensional behavior.

Here is shown, that a quantum vortex with a well-defined core can exist in a rather thick normal metal, proximized with a superconductor.