  Magnetic skyrmions are topological quasiparticles with great potential for
applications in future information storage and processing devices because of
their nanoscale size, high stability, and large velocity. Recently, the
high-frequency properties of skyrmions have been explored for magnon
nanodevices. Here we systematically study the dynamics of an isolated skyrmion
under voltage excitation through the voltage-controlled magnetic anisotropy
effect in a circular thin film. A theoretical model considering the
demagnetization energy, which has often been neglected or treated superficially
in previous skyrmion research but is demonstrated to have importance in
determining the skyrmion dynamic state, is developed. With our model, the
periodic oscillation of the skyrmion radius can be solved numerically with
similar precision compared to micromgnetic simulations, and the characteristic
frequency of the skyrmion breathing can be determined analytically with greater
precision than previous studies. Furthermore, we find that the breathing
skyrmion can be analogized as a modulator by investigating its linear
modulation functionality under sinusoidal-form voltage excitation. Different
from the conventional modulation system with complex CMOS circuits, this
skyrmion modulator device integrates with both the modulation and carrier wave
generation functionality, thus showing greater convenience and efficiency in
applications. Our findings can provide useful guidance for both theoretical and
experimental skyrmions research as well as the development of skyrmion-based
magnonic devices with significant potential applicability in future
communication system.
