"An independent characteristic length is called the coherence length. It is related to the Fermi velocity for the material and the energy gap associated with the condensation to the superconducting state. It has to do with the fact that the superconducting electron density cannot change quickly-there is a minimum length over which a given change can be made, lest it destroy the superconducting state. For example, a transition from the superconducting state to a normal state will have a transition layer of finite thickness which is related to the coherence length. Experimental studies of various superconductors have led to the following calculated values for these two types of characteristic lengths." Sourced from following [Characteristic Lengths in Superconductors] description here1 .
See table for various Coherence lengths of various materials in the linked article.
I have also added another great youtube video link that also explains Coherence length in greater detail. An interesting point is the way impurities added to a pure material can be inserted into a material to upset its electronic density and its superconducting waveform and cause the material to lose its superconducting properties. The more I research coherence length the more I understand it as the cooper electron pairing that takes place at superconducting temperatures and the resultant waveform that each substance gives rise to and the waveforms with wavelengths that stop the penetration of external magnetism.
