Dynamical superconducting states in hybrid structures superconductor/magnet

• Applicant: Professor Dr. Wolfgang Belzig
• Subject Area: Theoretical Condensed Matter Physics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 465140728

This project will explore the interaction of hybrid superconducting systems with quantum electromagnetic fields such as photons and magnons. This interaction strongly depends on the presence of spin-triplet superconductivity, topological Majorana states or collective Higgs modes in a superconductor, analogous to the Higgs boson in particle physics. The interest in these systems is stimulated by the recent progress in the fabrication of bilayers of superconductors and ferromagnetic insulators or metals providing a platform for a wide range of phenomena: topological superconducting states, coupled spin, heat and charge transport or spin pumping properties controllable by superconducting correlations.Interactions between differently ordered electronic systems, such as superconductors and magnets, have been thoroughly investigated in the past decades, but the focus so far has been on static or low-frequency properties. Simultaneously, the enormous progress in microwave quantum technology and low-temperature terahertz spectroscopy calls for an understanding of dynamical superconducting proximity effects and the interplay with dynamical modes, such as photons, magnons or superconducting order parameter collective oscillations. That is the focus of our project.First, we address the dynamical superconducting proximity effect. In contact with a magnetically ordered material unconventional superconductivity emerges close to the interface. Some prominent examples are triplet superconductivity, inhomogeneous phase states (helical superconducting states) and topological superconductivity. Exploiting superconductor/magnet hybrid structures in the field of spintronics implies a dynamical character of the magnetization. It entails a dynamical response of the proximity-induced unconventional superconductivity. However, both the fundamental aspects as well as prospects for applications of such dynamical unconventional superconductivity are hardly investigated until today, and we are planning to fill this gap. Our work plan includes investigations of dynamical triplet correlations in superconductor/ferromagnetic metal systems generated by spin waves and electromagnetic radiation as well as the response of inhomogeneous phase states in S/F hybrids to the magnetization dynamics in ferromagnets.Second, we focus on the coupling of topological Majorana modes and collective Higgs modes with magnons in (anti)ferromagnetic insulators. All these effects are fundamentally important in order to understand the behaviour of hybrid quantum systems consisting of superconductors, electromagnetic fields and spin waves. To this end, we will learn how to control the superconducting proximity effect with light, engineer and probe Majorana states and Higgs modes coupled with magnons. With that we will gain a deep insight into the dynamical properties of superconducting hybrid systems which potentially can be used in the rapidly developing quantum technologies.

• DFG Programme: Research Grants
• International Connection: Finland, Russia
• Partner Organisation: Russian Science Foundation, until 3/2022
• Cooperation Partners: Alexander Bobkov, Ph.D., until 3/2022; Irina Bobkova, Ph.D., until 3/2022; Zhanna Devizorova, Ph.D., until 3/2022; Andrei Mazanik, Ph.D., until 3/2022; Ilhom Rahmonov, Ph.D., until 3/2022; Mikhail Silaev, Ph.D.