The superconductor-ferromagnet-superconductor φ0 junction provides a direct coupling between Josephson phase and magnetic moment of ferromagnetic barrier. We demonstrate an appearance of additional fractional subharmonic steps in the IV-characteristics of φ0 junction under external electromagnetic radiation due to spin-orbit coupling. An origin of subharmonic steps is related to the locking of magnetic moment precession to the Josephson oscillations. We prove that the positions of those steps follow a continued fraction algorithm.
@article{arxiv.1905.09672,
title = {Devil's staircase structures in $\varphi_{0}$ junction},
author = {M. Nashaat and Yu. M. Shukrinov and A. Y. Ellithi and Th. M. El Sherbini},
journal= {arXiv preprint arXiv:1905.09672},
year = {2019}
}