In Landau mean-field theory, at temperatures T near the superconducting critical temperature Tc , ξ(T) ∝ (1-T/Tc)−1/2. Up to a factor of , it is equivalent characteristic exponent describing a recovery of the order parameter away from a perturbation in the theory of the second order phase transitions.
In some special limiting cases, for example in the weak-coupling BCS theory of isotropic s-wave superconductor it is related to characteristic Cooper pair size:
where is the reduced Planck constant, is the mass of a Cooper pair (twice the electron mass), is the Fermi velocity, and is the superconducting energy gap. The superconducting coherence length is a measure of the size of a Cooper pair (distance between the two electrons) and is of the order of cm. The electron near or at the Fermi surface moving through the lattice of a metal produces behind itself an attractive potential of range of the order of cm, the lattice distance being of order cm. For a very authoritative explanation based on physical intuition see the CERN article by V.F. Weisskopf.