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Calculated magnetization curve for a superconducting slab, based on Bean's model. The superconducting slab is initially at H = 0. Increasing H to critical field H* causes the blue curve; dropping H back to 0 and reversing direction to increase it to -H* causes the green curve; dropping H back to 0 again and increase H to H* causes the orange curve.
In the same experiment, he also observed the superfluid transition of helium at 2.2 K, without recognizing its significance. The precise date and circumstances of the discovery were only reconstructed a century later, when Onnes's notebook was found. [10] In subsequent decades, superconductivity was observed in several other materials.
This effect suggests that superconductivity is related to vibrations of the lattice. This is incorporated into BCS theory, where lattice vibrations yield the binding energy of electrons in a Cooper pair. Little–Parks experiment [15] - One of the first [citation needed] indications to the importance of the Cooper-pairing principle.
The experiment demonstrated for the first time that superconductors were more than just perfect conductors and provided a uniquely defining property of the superconductor state. The ability for the expulsion effect is determined by the nature of equilibrium formed by the neutralization within the unit cell of a superconductor.
Yttrium barium copper oxide (YBCO) is a family of crystalline chemical compounds that display high-temperature superconductivity; it includes the first material ever discovered to become superconducting above the boiling point of liquid nitrogen [77 K (−196.2 °C; −321.1 °F)] at about 93 K (−180.2 °C; −292.3 °F).
Schematic image of the Little–Parks experiment. The Little–Parks effect consists in a periodic variation of the T c with the magnetic flux, which is the product of the magnetic field (coaxial) and the cross sectional area of the cylinder. T c depends on the kinetic energy of the superconducting electrons.
In condensed matter physics, the resonating valence bond theory (RVB) is a theoretical model that attempts to describe high-temperature superconductivity, and in particular the superconductivity in cuprate compounds. It was first proposed by an American physicist P. W. Anderson and Indian theoretical physicist Ganapathy Baskaran in 1987.
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.