The critical state in a superconductor with periodic pins has properties similar to the pinch effect, known in plasma physics. It forms a terrace structure around the average flux density gradient, causing stratification of the transport current into the terrace edges where the flux density gradient is large. Regions of extremely high current thus interlace with regions of near zero current. The appearance of each new terrace inside the superconductor causes the magnetization to change abruptly at rational or periodic fields. This magnetization jump, a new quantum effect in superconductors, corresponds to the addition of one flux quantum threading the pin lattice unit cell.

• Received 28 September 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.2788