Critical density of states in the superconducting ceramic La1.8Sr0.2CuO4 in S–c–N point contacts

Measurement of the current–voltage characteristics of point contacts makes it possible to study the properties of individual crystallites in a superconducting ceramic. The critical current density in the superconducting regions of the ceramic La1.8Sr0.2CuO4, with a size of the order of several tens of angströms, is found to attain values of 108 A/cm2, which are of the same order of magnitude as the pair-breaking current density, as evaluated from the formulas of the standard theory of superconductivity.