Mesoscopic superconducting devices and circuits: Variable squid and superconducting micronet current amplifier

Abstract

Abstract Two mesoscopic superconducting devices based on micronets are introduced and analysed in the context of the Ginzburg-Landau theory. The 4-Port Variable Superconducting Quantum Interference Device with micronet leads is a passive device that can accurately measure magnetic fields, with a resolution dependent on its size and control current. The 3-Port Superconducting Micronet Current Amplifier (SMCA) with bulk leads is an active device, with a current controlled current gain determined by the input-current/applied-flux operating point and the relative lengths of the internal micronetwork branches. Analog and digital circuit applications of the SMCA are developed. The most significant is a differential amplifier-gradiometer that can measure small current differences, and small magnetic flux differences, less than the fluxoid quantum, Φ0 = 2.068 × 10−15 T-m2.