Current-induced suppression of superconductivity in a three-dimensional lattice of weakly linked indium grains in opal

Abstract

The current-voltage characteristics of the metal-dielectric composite have been investigated in the range of the resistive state near the superconducting transition temperature Tc. The composite structure can be represented as a face-centered cubic lattice, which involves a large number of weakly linked indium nanograins and is stabilized in structural cavities of opal. The response to microwave radiation is used to characterize the resistive state of the composite. The comparative investigation into the current-voltage characteristics and the response of the composite to microwave radiation makes it possible to conclude that the weak links are superconducting in the region of critical current (Ic) of the composite as a whole. The transition of weak links to the resistive state occurs at currents immediately preceding the transition of the composite from the resistive state to the ohmic state. The model of resistivity of the indium-opal composite is proposed on the basis of morphological examinations. According to this model, the energy dissipation in the resistive state is brought about by the quasi-discrete (due to the quantization of the magnetic flux in circuits of a three-dimensional lattice comprised of multiply connected grains) redistribution of transport current over the cross-section of composite.