Matching Effect in Superconducting Pb Inverse Opal.

The type II superconductivity was observed in highly periodic three-dimensional lead inverse opal prepared by infiltration of a melted Pb in blue (D=160 nm), green (D=220 nm) and red (D=300 nm) opals and following extraction of SiO$_{2}$ spheres by chemical etching. The onset of a broad phase transition ($\Delta $T=0.3 K) measured by temperature dependence of magnetic moment and AC resistivity was shifted from T$_{c}$=7.196 K for bulk Pb to T$_{c}$=7.29 K. Upper critical field H$_{c2}$ (3150 Oe) measured from high-field hysteresis loops exceeds the critical field for bulk lead (803 Oe) four fold. Well distinguished matching affect in field dependence of magnetic moment confirmed by periodic pinning in magneto-resistivity measurements is complying with the lattice parameter of inverse opal structure.