Conduction in granular aluminum near the metal-insulator transition

The electrical resistance has been measured on granular aluminum specimens with room-temperature resistivities between 1.5 ×{} 10^-3 and 1.3 ×{} 10^-1 {Ω} cm, from 0.3 K to room temperature, in magnetic fields up to 9 T. The results show the importance of electron correlation effects on both sides of the metal-insulator transition. The Mott hopping law is not observed in any specimen over the whole temperature range. The results suggest the possibility of superconductivity in the insulating phase.