Magnon spectrum in ferromagnets with a skyrmion
D. N. Aristov*+, S. S. Kravchenko*+, A. O. Sorokin*+
*Department of Physics, St. Petersburg State University, 199034 St. Petersburg, Russia
+Petersburg Nuclear Physics Institute, National Research Center "Kurchatov Institute", 188300 Gatchina, Russia
Abstract
The analysis of the spin wave excitations in two-dimensional isotropic
Heisenberg ferromagnet is performed with a single skyrmion in the ground
state. We employ the ideas of semiclassical quantization method, duly
modified for the use of the lattice model and Maleyev-Dyson boson
representation of spin operators. The resulting Schrödinger equation for
magnons describes the dispersion and wave functions of spin-wave excitations
with strictly non-negative spectrum. In contrast to usual ferromagnet, we
demonstrate the existence of three zero modes, corresponding to conformal
symmetries spontaneously violated by the skyrmion configuration.