Protected 0-pi states in SIsFS junctions for Josephson memory and logic

TL;DR

This paper investigates the current-phase relations in SIsFS Josephson junctions, revealing how barrier transparency and s-layer thickness influence 0 and π states, with implications for superconducting memory and logic devices.

Contribution

It uncovers how the CPR shape transforms with barrier transparency and s-layer thickness, identifying conditions for stable 0 and π states useful for memory and logic applications.

Findings

CPR consists of two independent branches for 0 and π states.

Decreasing s-layer thickness causes CPR shape transformation.

Difference in critical currents of branches can reach 10%.

Abstract

We study the peculiarities in current-phase relations (CPR) of the SIsFS junction in the region of $0$ to $\pi $ transition. These CPR consist of two independent branches corresponding to $0-$ and $\pi-$ states of the contact. We have found that depending on the transparency of the SIs tunnel barrier the decrease of the s-layer thickness leads to transformation of the CPR shape going in the two possible ways: either one of the branches exists only in discrete intervals of the phase difference $\varphi$ or both branches are sinusoidal but differ in the magnitude of their critical currents. We demonstrate that the difference can be as large as $10\%$ under maintaining superconductivity in the s layer. An applicability of these phenomena for memory and logic application is discussed.