Voltage-driven dynamics of $\varphi_0$-S/F/S Josephson junctions chains

TL;DR

This paper studies voltage-driven dynamics in chains of $$-S/F/S Josephson junctions, revealing new stable regimes and proposing IV-characteristics as a fingerprint for magnetoelectric coupling detection.

Contribution

It predicts the instability of conventional regimes in $$-S/F/S JJ chains and identifies new stable dynamic regimes influenced by $$, providing a method to detect and measure magnetoelectric coupling.

Findings

Identification of unstable regimes in $$-S/F/S JJ chains.

Discovery of new stable dynamic regimes influenced by $$.

Proposal of IV-characteristics as a fingerprint for magnetoelectric coupling.

Abstract

Superconductor/ferromagnet/superconductor Josephson junctions with anomalous phase shift $\varphi_0$ ($\varphi_0$-S/F/S JJs) implement a coupling between the superconducting phase and the spin degrees of freedom. Here we investigate the dynamics of voltage-biased coupled chains of $\varphi_0$-S/F/S JJs and predict that the presence of $\varphi_0$ makes the conventional regime corresponding to the linear growth of the superconducting phase at each of the junctions and oscillating Josephson current unstable. New stable regimes are found and investigated. The changes of the dynamic behavior are clearly seen in the IV-characteristics of the system and can serve as a fingerprint of the presence of the magnetoelectric coupling $\varphi_0$. Moreover, the collective magnetic excitations of the chains of $\varphi_0$-S/F/S JJs, which were reported by G.A. Bobkov {\it et. al.} [JETP Lett. {\bf 119}, 251 (2024)] also manifest themselves in the IV-characteristics. This provides a method for their experimental detection and direct measurement of the constant quantifying the strength of the coupling between the superconducting phase and the spin degrees of freedom.