Interferometric evidence of non-volatile anomalous phase shifts in exchange-spin-split Josephson supercurrent diodes

TL;DR

This paper provides phase-sensitive evidence of spontaneous time-reversal symmetry breaking in Rashba-type Josephson junctions, demonstrating how proximity effects and material choices influence non-volatile anomalous phase shifts and diode efficiencies.

Contribution

It introduces direct superconducting quantum interferometry measurements of {}_0 shifts in various material-based JJs, revealing how proximity effects control zero-field diode behavior.

Findings

Ta and W JJs show diode efficiencies of ~17% and ~5% at 2 K.

Diode polarity in Ta and W JJs is reversed compared to Pt JJs.

Pd JJs exhibit large diode efficiency (~15%) due to magnetic susceptibility.

Abstract

The recent realization of zero-field, polarity-reversible supercurrent rectification in proximity-magnetized Rashba-type Pt Josephson junctions (JJs) enables the development of superconducting logic circuits and cryogenic memory applications. Here, we demonstrate a non-volatile anomalous phase shift {\phi}_0 directly probed via superconducting quantum interferometry, providing phase-sensitive evidence of spontaneous time-reversal symmetry breaking in these Rashba-type systems. By replacing the Pt barrier with 5d or 4d element layers exhibiting different (para-)magnetic susceptibilities, spin-orbit coupling strengths, and electronic band structures, we elucidate the role of proximity effects in governing zero-field diode behavior. Ta (W) JJs exhibit zero-field diode efficiencies of ~17% (~5%) at 2 K, which are slightly (significantly) lower than those of Pt JJs. Notably, the diode polarity in Ta and W JJs is reversed relative to Pt JJs. Combined with the large zero-field diode efficiency (~15% at 2 K) observed in highly magnetic-susceptible Pd JJs, these results show that non-volatile {\phi}_0 and, consequently, zero-field diode performance can be tuned through proximity engineering of interfacial magnetic ordering and Rashba spin-orbit interaction.