Features of superconducting transition in nanocomposite consisting of “insulating matrix (porous alkali-borosilicate glass)” – “granular metallic filler (indium)”

Patterns in temperature and magnetic field behavior of the electrical resistance of nanocomposite consisting of “insulating matrix (7 nm-pore alkali-borosilicate glass)” – “granular metallic filler (indium)” (PG7+In) has been found and analyzed in the vicinity of superconducting transition. Insulating behavior in the electrical resistivity has been observed in a normal state. External magnetic field shifts the transition to lower temperatures and the same time gradually strengths the insulating behavior above the superconducting transition. Hopping conductivity mechanism developed for the granular conductor systems can be responsible for the insulating behavior in normal-state electrical resistance. Electron hopping in the granular conductor system is realized as tunneling of electrons through intergranular contacts between the metallic granules. The superconducting transition has been found to be rather broad. Broadening in the superconducting transition can be attributed to fluctuation conductivity. Above the superconducting transition, the Aslamazov-Larkin contribution to the conductivity characteristic for three-dimensional systems has been found to be main correction to the conductivity.