Breathing skyrmions in chiral antiferromagnets

Breathing oscillations of skyrmions in chiral antiferromagnets can be excited by a brief modification of the Dzyaloshinskii-Moriya interaction or magnetocrystalline anisotropy strength. We employ an adiabatic approx-imation and derive a formula for the potential energy that directly implies breathing oscillations. We study the nonlinear regime and the features of larger-amplitude oscillations, and we verify the validity of the adiabatic approximation. We show that there is a maximum amplitude supported by the potential. As a consequence, we predict theoretically and observe numerically skyrmion collapse and subsequent annihilation events due to excitation of large-amplitude breathing oscillations. The process is efficient when the skyrmion is mildly excited so that its radius initially grows, while the annihilation event is eventually induced by the internal breathing dynamics. We reveal the counterintuitive property that the skyrmion possesses a nonzero kinetic energy at the instance of its annihilation. Finally, the frequency of small-amplitude breathing oscillations is determined.