Scattering of vortex pairs in 2D easy-plane ferromagnets
A.S. Kovalev
Institute for Low Temperature Physics and Engineering,
47 Lenin Ave., 61164 Kharkov, Ukraine
S. Komineas and F.G. Mertens
Physikalisches Institut, Universitaet Bayreuth D-95440 Bayreuth, Germany
Abstract
Vortex-antivortex pairs in 2D easy-plane ferromagnets have characteristics
of solitons in two dimensions.
We investigate numerically and analytically the dynamics
of such vortex pairs. In particular
we simulate numerically the head-on collision of two pairs
with different velocities for a
wide range of the total linear momentum of the system.
If the momentum difference of the two pairs is small, the vortices
exchange partners, scatter at an angle depending on this difference,
and form two new identical pairs.
If it is large, the pairs pass through each other without
losing their identity.
We also study head-tail collisions.
Two identical pairs moving in the same direction are bound into a moving
quadrupole in which the two vortices as well as the two antivortices
rotate around each other.
We study the scattering processes also analytically in the
frame of a collective variable theory,
where the equations of motion for a system of four vortices constitute
an integrable system. The features of the different collision
scenarios are fully reproduced by the theory.
We finally compare some aspects of the present soliton scattering
with the corresponding situation in one dimension.