Magnonskyrmion scattering in chiral magnets
Abstract
Chiral magnets support topological skyrmion textures due to the DzyaloshinskiiMoriya spinorbit interaction. In the presence of a sufficiently large applied magnetic field, such skyrmions are largeamplitude excitations of the fieldpolarized magnetic state. We investigate analytically the interaction between such a skyrmion excitation and its smallamplitude fluctuations, i.e., the magnons in a clean twodimensional chiral magnet. The magnon spectrum is found to include two magnonskyrmion bound states corresponding to a breathing mode and, for intermediate fields, a quadrupolar mode, which will give rise to subgap magnetic and electric resonances. Due to the skyrmion topology, the magnons scatter from an AharonovBohm flux density that leads to skew and rainbow scattering, characterized by an asymmetric differential cross section with, in general, multiple peaks. As a consequence of the skew scattering, a finite density of skyrmions will generate a topological magnon Hall effect. Using the conservation law for the energymomentum tensor, we demonstrate that the magnons also transfer momentum to the skyrmion. As a consequence, a magnon current leads to magnon pressure reflected in a momentumtransfer force in the Thiele equation of motion for the skyrmion. This force is reactive and governed by the scattering cross sections of the skyrmion; it causes not only a finite skyrmion velocity but also a large skyrmion Hall effect. Our results provide, in particular, the basis for a theory of skyrmion caloritronics for a dilute skyrmion gas in clean insulating chiral magnets.
 Publication:

Physical Review B
 Pub Date:
 September 2014
 DOI:
 10.1103/PhysRevB.90.094423
 arXiv:
 arXiv:1405.1568
 Bibcode:
 2014PhRvB..90i4423S
 Keywords:

 75.78.n;
 75.70.Kw;
 75.30.Ds;
 75.76.+j;
 Domain structure;
 Spin waves;
 Condensed Matter  Strongly Correlated Electrons
 EPrint:
 19 pages, 13 figures