BEGIN:VCALENDAR VERSION:2.0 PRODID:Data::ICal 0.22 BEGIN:VEVENT DESCRIPTION:Charles Reichhardt\, Los Alamos National Lab\n\n
Si
nce the initial discovery of skyrmion lattices in chiral magnets [1]\, the
re has been a tremendous growth in this field as an increasing number of c
ompounds are found to have extended regions of stable skyrmion lattices [2
] even close to room temperature [3]. \; These systems have significan
t promise for applications due to their size scale and the low currents or
drives needed to move the skyrmions [4]. \; Another interesting aspec
t of skyrmions is that the equations of motion have significant non-dissip
ative terms or a Magnus effect which makes them unique in terms of collect
ive driven dynamics as compared to other systems such as vortex lattices i
n type-II superconductors\, sliding charge density waves\, and frictional
systems. \; We examine the driven dynamics of skyrmions interacting wi
th random and periodic substrate potentials using both continuum based mod
elling and particle based simulations. In clean systems we examine the ran
ge in which skyrmion motion can be explored as a function of the magnetic
field and current and show that there can be a current-induced creation or
destruction of skyrmions. \; In systems with random pinning we find t
hat there is a finite depinning threshold and that the Hall angle shows a
strong dependence on the disorder strength. We also show that features in
the transport curves correlate with different types of skyrmion flow regim
es including a skyrmion glass depinning/skyrmion plastic flow region as we
ll as a transition to a dynamically reordered skyrmioncrystal at higher dr
ives. We find that increasing the Magnus term produces a low depinning thr
eshold which is due to a combination of skyrmions forming complex orbits w
ithin the pinning sites and \; skyrmion-skyrmion scattering effects.&n
bsp\; If the skyrmions are moving over a periodic substrate\, with increas
ing drive the Hall angle changes in quantized steps which correspond to pe
riodic trajectories of the skyrmion that lock to symmetry directions of th
e substrate potential.
\n
\n[1] S. Muhlbauer et al Science 323 9
15 (2009).
\n[2] X. Z. \; Yu et al. Nature 465\, 901&ndash\;904 (
2010).
\n[3] X.Z. Yu et al Nature Materials\, 10\, 106 (2011).
\
n[4] A. Fert\, V. Cros\, and J. Sampaio Nature Nanotechnology 8\, 152 (201
3).