Superluminal Propagation of Composite Collective Modes in Superconductor-Ferromagnet Heterostructures

Abstract

Superconductor/ferromagnet/superconductor Josephson junctions are paradigmatic systems for studying the delicate interplay of superconductivity and magnetism via proximity effects as well as their composite excitations. Here, we analyse the collective modes (CM) in such a heterostructure by taking into account the interplay between the de-magnetisation field $H_{dem}$ and the field caused by the anisotropy of the ferromagnet $H_{an}$, which was previously neglected. It turns out that the spectrum of composite collective modes, $\omega (k)$, has a qualitatively different form in the case of $H_{dem}<H_{an}$ and of $H_{dem}>H_{an}$. In the first case, the dependence $\omega (k)$ has the same form as in previous studies, whereas in the second case, the spectrum looks completely different. In particular, for moderate or weak anisotropy in ferromagnet the group velocity of collective modes demonstrates inflection point where the group velocity become infinite and is superluminal. Furthermore, this point separates purely real and complex-conjugate solutions for the collective modes and is also {\it exception point}. We show that the difference of the CMs spectra can be revealed by Fiske experiment, i.\,e.\,by measuring the $I-V$ characteristics in the presence of magnetic field and voltage.

7 pages, 3 figures

References in corpus (18)

• Electrodynamics of Correlated Electron Materials
• Static and dynamic properties of 0, pi, and 0-pi ferromagnetic tunnel Josephson Junctions
• Skyrmion-(Anti)Vortex Coupling in a Chiral Magnet-Superconductor Heterostructure
• Observation and control of hybrid spin-wave-Meissner-current transport modes
• Interaction of a Nanomagnet with a Weak Superconducting Link
• Approaching to the deep-strong photon-to-magnon coupling
• Ferromagnetic Materials for Josephson π Junctions
• Magnetoelectric effects in Josephson junctions
• Magnetization dynamics in proximity-coupled superconductor-ferromagnet-superconductor multilayers. Part II
• Ultrastrong magnon-photon coupling and entanglement in superconductor/ferromagnet nanostructures
• Anomalous Gilbert Damping and Duffing Features of the SFS {\boldmath ${\phi }_0$} Josephson Junction
• Magnon-Cooparons in magnet-superconductor hybrids
• Interplay between nematicity and Bardasis-Schrieffer modes in the short-time dynamics of unconventional superconductors
• Manipulating Magnetic Moments by Superconducting Currents
• Phase dynamics of tunnel Al-based ferromagnetic Josephson junctions
• Collisionless dynamics of superconducting gap excited by spin-splitting field
• Collective magnetic and plasma excitations in Josephson $\psi$ junctions
• Antiferromagnetic resonances in superconductor-ferromagnet multilayers

Cited by in corpus (1)

• Electromagnetic Proximity Effect: Superconducting Magnonics and Beyond