Main field of study:  010700 Physics
Area of specialisation: Statistical theory of inhomogeneous systems
Department of Statistical Physics
Scientific advisor: Doctor of Physical and Mathematical Sciences, Prof. D.N. Aristov
Reviewer: Doctor of Physical and Mathematical Sciences, Prof. V. M. Uzdin 

Semiclassical analysis of the magnon spectrum in ferromagnet with the skyrmion ground state
Kravchenko Sergey

We attempt to analyze the magnon spectrum of ferromagnets with one skyrmion in the ground state, using the semiclassical approach. Starting from the lattice model, we first allow the average local spin be arbitrarily directed, with neighboring spins differing only slightly in their direction. Using the variational procedure, and seeking analytical helical solution, we arrive at a single Belavin-Polyakov skyrmion. At the second stage we employ bosonic representation for the spin operators and the quasiclassical 1/S approach.
Restricting our consideration to the linear spin-wave theory, we arrive at the analog of Shroedinger equation, describing the spectrum of magnons in the presence of one skyrmion.  Analytical solutions with zero energy are found, further numerical studies are suggested.

The list of the publications
1. S. Kravchenko. Semiclassical analysis of the spectrum of ferromagnet with the skyrmion ground state // Vestnik of Saint Petersburg university 2014.