  Surface plasmons in two-dimensional (2D) electron systems have attracted
great attention for their promising light-matter applications. However, the
excitation of a surface plasmon, in particular, transverse-electric (TE)
surface plasmon, remains an outstanding challenge due to the difficulty to
conserve energy and momentum simultaneously in the normal 2D materials. Here we
show that the TE surface plasmons ranging from gigahertz to terahertz regime
can be effectively excited and manipulated in a hybrid dielectric, 2D material
and magnet structure. The essential physics is that the surface spin wave
supplements an additional freedom of surface plasmon excitation and thus
greatly enhances the electric field in the 2D medium. Based on widely-used
magnetic materials like yttrium iron garnet (YIG) and manganese difluoride
($\mathrm{MnF}_2$), we further show that the plasmon excitation manifests
itself as a measurable dip in the reflection spectrum of the hybrid system
while the dip position and the dip depth can be well controlled by the electric
gating on the 2D layer and an external magnetic field. Our findings should
bridge the fields of low-dimensional physics, plasmonics and spintronics and
open a novel route to integrate plasmonic and spintronic devices.
