Magnetic-field oscillations of the critical current and the pinning force in PbTe/PbS semiconductor superlattices and YBa2Cu3O7–δ films

The magnetic-field dependences of the critical current Ic and the pinning force Fp in single-crystal semiconductor PbTe/PbS superlattices on KCl and YBa2Cu3O7–δ films in magnetic fields oriented perpendicular to the plane of the samples or parallel to the current were investigated. Oscillations of Ic and Fp were observed for superlattices with a parallel orientation of the magnetic field and with two directions of the field for the YBa2Cu3O7–δ film. A model was proposed for the vortex structures which correspond to extrema of the pinning force in superlattices. It was shown that the single points (extrema and points of inflection) of the field dependences of Fp for superlattices and a YBa2Cu3O7–δ film appear for critical values of the magnetic field equal to Hcr = (p/q)H0, where p and q are integers, H0 = 838.37 Oe, and H0 = ch/π eR02 is determined by the length R0 = 88.607 nm, somewhat less than the reciprocal of the Rydberg constant R∞ = me4/πħ3c (R∞−1 = 91.127 nm). It was inferred on the basis of published data that the temperature and magnetic-field dependences of the properties of superlattices and HTSC materials follow general laws.