Dynamics of skyrmions in metallic chiral magnets

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Date/Time:Thursday, 26 Sep 2013 - Saturday, 28 Sep 2013
Location:PHYSICS Hall Room 3
Channel:Condensed Matter Physics
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Zhi-seng Lin Theoretical Division, Los Alamos National Laboratory, USA

Stable topological excitations such as domain walls, vortices are ubiquitous in condensed matter systems and are responsible for many emergent phenomena. Recently a new mesoscopic spin texture called skyrmion with radius about 10 ~100 nm was discovered experimentally in certain conducting or insulating magnets in 2009. In the temperature-magnetic field phase diagram, skyrmions form a triangular lattice in the low temperature and intermediate magnetic field region in thin films. In metallic magnets, skyrmions can be driven by a spin polarized current. The threshold current density to depin skyrmions is about 100 A/cm^2, which is 4-5 order of magnitudes weaker than that for magnetic domain walls. The low depinning current makes skyrmions extremely promising for application in spintronics, such as information storage.

In this talk, first I will attempt to summarize the experiments and to present an overview on skyrmions. Then I will talk about our recent work on skyrmions. We derived an equation of motion of skyrmions by treating them as rigid particles, based on which the weak pinning of skyrmion can be explained. I will also discuss the dynamical phase transitions for skyrmions and show that skyrmions can be created and destroyed dynamically by current. Finally I will compare skyrmions with other topological objects such as vortices in type II superconductors.

*This work is in collaboration with Charles Reichhardt, Cristian D. Batista and Avadh Saxena.