London penetration depth

Description

In superconductors, the London penetration depth (usually denoted as λ or λ_L) characterizes the distance to which a magnetic field penetrates into a superconductor and becomes equal to e−1 times that of the magnetic field at the surface of the superconductor. Typical values of λ_L range from 50 to 500 nm.

The London penetration depth results from considering the London equation and Ampère’s circuital law.

The London penetration depth can be seen as the distance across in which the magnetic field becomes e times weaker.