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London penetration depth



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

Typical values of λL 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 B0 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

i.e. λL 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.

see also

 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "London_penetration_depth". A list of authors is available in Wikipedia.
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