Shift of the maxima of the critical currents of different polarity relative to the zero magnetic flux along the flux axis in a superconducting asymmetric aluminum ring

TL;DR

This study investigates the rectification of ac voltage in asymmetric superconducting aluminum rings, revealing a temperature-dependent shift in critical current maxima due to phase differences, and proposes a new model explaining this phenomenon.

Contribution

It introduces a novel model for the temperature-dependent phase shift in asymmetric superconducting rings, explaining the critical current maxima shift.

Findings

The maxima of critical currents are shifted relative to zero flux in opposite directions.

The shift depends on temperature and differences in critical temperatures of the semirings.

The proposed model accurately describes the temperature-dependent shift and resolves previous measurement contradictions.

Abstract

We measured the rectification of an ac voltage in a structure of superconducting circularly-asymmetric aluminum rings in series, permeated with a magnetic flux and biased with a low-frequency alternating current (without a dc component). This rectification is due to the shift of the maxima of the critical currents of different polarity relative to the zero flux in opposite directions along the flux axis in the asymmetric ring. For the first time, we propose a model for a temperature-dependent phase shift equal to difference between dimensionless kinetic inductances of wide and narrow semirings having the same length and thickness. The shift is not zero in the case of different critical currents densities in both semirings. This is possible only in a situation of different critical temperatures of both semirings. The model describes well the temperature-dependent shift of the maxima of the critical currents, answers the long-standing mysterious challenge of the shift and removes extremely strange contradiction between the results of different measurements, previously found in circularly-asymmetric aluminum structures.