Induction of dc voltage, proportional to the persistent current, by external ac current on system of inhomogeneous superconducting loops

TL;DR

This paper reports the observation of a dc voltage induced by external ac current in asymmetric superconducting loops, which depends periodically on magnetic flux and is interpreted as a rectification effect related to persistent currents.

Contribution

The study demonstrates a new rectification phenomenon in superconducting loops caused by external ac current, with detailed analysis of its dependence on magnetic flux and system configuration.

Findings

Dc voltage oscillates with magnetic flux quantum period.

Amplitude of voltage depends on ac current amplitude, not frequency.

System of multiple loops enhances the induced dc voltage.

Abstract

A dc voltage induced by an external ac current is observed in system of asymmetric mesoscopic superconducting loops. The value and sign of this dc voltage, like the one of the persistent current, depend in a periodical way on a magnetic field with period corresponded to the flux quantum within the loop. The amplitude of the oscillations does not depend on the frequency of the external ac current (in the investigated region 100 Hz - 1 MHz) and depends on its amplitude. The latter dependence is not monotonous. The observed phenomenon of rectification is interpreted as a consequence of a dynamic resistive state induced by superposition of the external current and the persistent current. It is shown that the dc voltage can be added in system of loops connected in series: the dc voltage oscillations with amplitude up to 0.00001 V were observed in single loop, up to 0.00004 V in a system of 3 loops and up to 0.0003 V in a system of 20 loops.