Skyrmions: Topological Excitations and Novel Computing Paradigms

Stable topological  excitations such  as domain  walls and vortices are  ubiquitous in condensed   matter as  well as  high  energy  physics and  are  responsible  for  many emergent  phenomena. In 2009 a new mesoscopic spin texture called skyrmion was discovered  experimentally  in  certain  conducting  and  insulating  magnets.  It  is  now  believed to exist in Bose-Einstein condensates, 2D electron gases, superconductors, nematic liquid crystals among many other systems. This topological excitation was originally proposed by Tony Skyrme in 1958 in a nonlinear field theory of baryons. In the temperature-magnetic field phase diagram of chiral magnets, 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 while in insulating magnets by magnons. The threshold current density to depin  skyrmions  is  4  to  5  orders  of  magnitude  weaker  than  that  for  magnetic domain walls. The low depinning current makes skyrmions extremely promising for applications in spintronics.  I will first attempt to summarize the experiments and present  an  overview  on  skyrmions.  Then I will demonstrate how the interplay of Dzyaloshinskii-Moriya (DM) interaction and magnetic anisotropy stabilizes skyrmions. New ways of computing that arise from specific spintronics applications due to the underlying spin-orbit coupling and skyrmionics will also be explored in this context. 
 
About the research of the speaker: http://cnls.lanl.gov/external/people/Avadh_Saxena.php
 
Host: Jean-Philippe Ansermet