Buzdin, Shapiro and Chimera Steps in $\varphi_0$ Josephson Junctions

TL;DR

This paper explores novel resonance phenomena in $\

Contribution

It introduces Buzdin and Chimera steps as new locking phenomena in $\\varphi_0$ Josephson junctions influenced by magnetic and electric radiation components.

Findings

Identification of Buzdin steps driven by magnetic radiation.

Discovery of Chimera steps when both electric and magnetic components are present.

Significant impact of spin-orbit coupling on step amplitudes.

Abstract

The unique resonance and locking phenomena in the superconductor-ferromagnet-superconductor $\varphi_0$ Josephson junction under external electromagnetic radiation are demonstrated when not just the electric but also the magnetic component of external radiation is taken into account. Due to the coupling of superconductivity and magnetism in this system, the magnetic moment precession of the ferromagnetic layer caused by the magnetic component of external radiation can lock the Josephson oscillations, which results in the appearance of a particular type of steps in the current-voltage characteristics, completely different from the well-known Shapiro steps. We call these steps the Buzdin steps in the case when the system is driven only by the magnetic component and the Chimera steps in the case when both magnetic and electric components are present. Unlike the Shapiro steps where the magnetization remains constant along the step, here it changes though the system is locked. The spin-orbit coupling substantially contributes to the amplitude, i.e., the size of these steps. Dramatic changes in their amplitudes are also observed at frequencies near the ferromagnetic resonance. Combinations of the Josephson and Kittel ferromagnetic resonances together with different types of locking pronounced in dynamics and current-voltage characteristics make the physics of this system very interesting and open up a series of new applications.