Persistent Supercurrents and Perfect Diamagnetism

A B-field does not exist in the interior of superconductors. Since B = + M) = 0, 

Xm = M/H=—l. which implies that superconductors are perfect diamagnetic materials. This diamagnetism results from surface currents that circulate to cancel external fields. These supercurrents are given by 

Ms is the number of electrons in the superconducting state kc/m is the momentum of the center of mass of the Cooper pair 

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