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Andreev reflection, named after the Russian physicist Alexander F. Andreev, is a type of particle scattering which occurs at interfaces between a superconductor (S) and a normal state material (N). It is a charge-transfer process by which normal current in N is converted to supercurrent in S.
In type-1.5 superconductors these vortices have long-range attractive, short-range repulsive interaction. As a consequence a type-1.5 superconductor in a magnetic field can form a phase separation into domains with expelled magnetic field and clusters of quantum vortices which are bound together by attractive intervortex forces.
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. It describes how electrons in one material take on the ...
[1] [2] It is an example of a macroscopic quantum phenomenon, where the effects of quantum mechanics are observable at ordinary, rather than atomic, scale. The Josephson effect has many practical applications because it exhibits a precise relationship between different physical measures, such as voltage and frequency, facilitating highly ...
The table below shows some of the parameters of common superconductors.X:Y means material X doped with element Y, T C is the highest reported transition temperature in kelvins and H C is a critical magnetic field in tesla.
The size of the critical current (which can be as large as 100 amperes in a 1-mm wire) depends on the nature and geometry of the specimen and is related to whether the magnetic field produced by the current exceeds the critical field at the surface of the superconductor. [2]
Low-temperature superconductor (LTS) wires are made from superconductors with low critical temperature, such as Nb 3 Sn (niobium–tin) and NbTi (niobium–titanium). Often the superconductor is in filament form in a copper or aluminium matrix which carries the current should the superconductor quench for any reason.
Phase diagram (B, T) of a type I superconductor : if B < B c, the medium is superconducting. T c is the critical temperature of a superconductor when there is no magnetic field. The interior of a bulk superconductor cannot be penetrated by a weak magnetic field, a phenomenon known as the Meissner effect. When the applied magnetic field becomes ...