Phase-quantum tunnel device

Granular superconductor (GS) consists of material in which metal grains are isolated by insulating barriers. In the material, relatively strong superconductivity is found to coexist with low normal conductivity. The present investigation is concerned with a theoretical study of granular superconductivity. Aspects of electric charge relaxation in GS are considered along with the concept of a Theta-superconductor and an N-superconductor, the condensation of phaseons in an N-superconductor, a phaseon-tunneling device, and an oscillation mode conjugate to Josephson plasma oscillations. A description is given of a number of experiments conducted at 4.2 K, taking into account the microwave-current response of a single device, the current-voltage characteristics of a dc-SQUID structure, the interference effect in a U-shaped structure, and a three-terminal device. It is found that a macroscopic quantum effect which is different from the Josephson effect can be observed.