Interplay of spin waves and surface plasmons in hybrid magnet/2D material structures

Understanding the interaction of light and matter is an important topic in condensed matter physics. Light can induce electronic oscillations on metal surfaces, known as surface plasmons, which have important applications in electromagnetic wave amplification and sensing. Although surface plasmons in the visible and infrared regions have been widely studied, how to generate low-frequency plasmons with desirable polarity is still an outstanding challenge. Here, by exploring the transport properties of electromagnetic waves in a two-dimensional (2D) material/magnetic film composite system, we found that the surface spin waves excited in the magnet can break the excitation bottleneck of transverse electric mode surface plasmons in the 2D materials. The joint excitation of spin waves and surface plasmons will take away part of the electromagnetic energy, thus showing an obvious valley in the reflection spectrum of the system, which may be feasible to be detected in experiments. Furthermore, we found that spin waves and surface plasmons in 2D materials will form an anticrossing energy level near the resonance frequency. Thanks to the tunability of the 2D system, the coupling strength can be effectively controlled through electric gating technology and reaches the strong coupling regime. Our series of results extend the current research scope of magnon spintronics, and also provide new ideas for the development of the interdisciplinary fields of spintronics, nanophotonics and low-dimensional physics.