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The penetration depth is determined by the superfluid density, which is an important quantity that determines T c in high-temperature superconductors. If some superconductors have some node in their energy gap, the penetration depth at 0 K depends on magnetic field because superfluid density is changed by magnetic field and vice versa. So ...
There are two London equations when expressed in terms of measurable fields: =, =. Here is the (superconducting) current density, E and B are respectively the electric and magnetic fields within the superconductor, is the charge of an electron or proton, is electron mass, and is a phenomenological constant loosely associated with a number density of superconducting carriers.
The penetration depth of X-rays in water as function of photon energy. Penetration depth is a measure of how deep light or any electromagnetic radiation can penetrate into a material. It is defined as the depth at which the intensity of the radiation inside the material falls to 1/e (about 37%) of its original value at (or more properly, just ...
The ratio = /, where is the London penetration depth, is known as the Ginzburg–Landau parameter. Type-I superconductors are those with 0 < κ < 1 / 2 {\displaystyle 0<\kappa <1/{\sqrt {2}}} , and type-II superconductors are those with κ > 1 / 2 {\displaystyle \kappa >1/{\sqrt {2}}} .
For most superconductors, the London penetration depth is on the order of 100 nm. The Meissner effect is sometimes confused with the kind of diamagnetism one would expect in a perfect electrical conductor: according to Lenz's law , when a changing magnetic field is applied to a conductor, it will induce an electric current in the conductor that ...
The penetration depth sets the exponential law according to which an external magnetic field decays inside the superconductor. The original idea on the parameter κ belongs to Landau. The ratio κ = λ / ξ is presently known as the Ginzburg–Landau parameter.
Ginzburg–Landau theory introduced the superconducting coherence length ξ in addition to London magnetic field penetration depth λ. According to Ginzburg–Landau theory, in a type-II superconductor / > /. Ginzburg and Landau showed that this leads to negative energy of the interface between superconducting and normal phases.
More exactly, magnetic field H penetrates into a superconductor over a small distance called London's magnetic field penetration depth (denoted λ L and usually ≈ 100 nm). The screening currents also flow in this λ L -layer near the surface, creating magnetization M inside the superconductor, which perfectly compensates the applied field H ...