London penetration depth

In superconductivity, London penetration depth (usually denoted as $λ$ or $λ L$ ) characterizes the typical distance to which a weak magnetic field penetrates into a superconductor.

Typical values of

λ L

are between 50 and 500nm. Deep inside a superconductor the magnetic field is zero (Meissner effect). For example, if one considers a superconducting semi-space at

x > 0

, and weak external magnetic field

B 0

applied along

z

-direction in the empty space

x < 0

, then inside the superconductor the magnetic field is given by $B(x)=B_0\exp\left(-\frac{x}{\lambda_L}\right),$

Additional recommended knowledge

Don't let static charges disrupt your weighing accuracy

Essential Laboratory Skills Guide

Daily Sensitivity Test

i.e. $λ L$ is the distance across which magnetic field becomes $e$ times weaker. The above expression follows from the solution of the London equation with proper boundary conditions.

London penetration depth

Additional recommended knowledge

Don't let static charges disrupt your weighing accuracy

Essential Laboratory Skills Guide

Daily Sensitivity Test

see also

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