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If a BCS superconductor with a ground state consisting of Cooper pair singlets (and center-of-mass momentum q = 0) is subjected to an applied magnetic field, then the spin structure is not affected until the Zeeman energy is strong enough to flip one spin of the singlet and break the Cooper pair, thus destroying superconductivity (paramagnetic or Pauli pair breaking).
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.
It commemorates the Theory of Superconductivity developed here by John Bardeen and his students, for which they won a Nobel Prize for Physics in 1972. Microscopic theory of superconductivity In physics , the Bardeen–Cooper–Schrieffer ( BCS ) theory (named after John Bardeen , Leon Cooper , and John Robert Schrieffer ) is the first ...
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.
Superconductivity was first discovered in solid mercury in 1911 by Heike Kamerlingh Onnes and Gilles Holst, who had developed new techniques to reach near-absolute zero temperatures. [1] [2] [3] In subsequent decades, superconductivity was found in several other materials; In 1913, lead at 7 K, in 1930's niobium at 10 K, and in 1941 niobium ...
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.
Based on Landau's previously established theory of second-order phase transitions, Ginzburg and Landau argued that the free energy density of a superconductor near the superconducting transition can be expressed in terms of a complex order parameter field () = | | (), where the quantity | | is a measure of the local density of superconducting electrons () analogous to a quantum mechanical wave ...
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.