Title: “Skyrmion in Helimagnets"

 

Abstract: Common magnets, such as refrigerator magnets and recorded bits in your hard disk, have aligned magnetic moments as compelled by the exchange interaction that causes ferromagnetism in the first place. Helimagnets are new types of magnets that exist in materials with broken inversion (non-centrasymmetric) symmetry, which enables the Dzyaloshinskii-Moriya interaction (DMI) to favor moments to be perpendicular to each other.  As a result of the competition, the ground state of a helimagnet is a spin helix and equally fascinating, the existence of skyrmion in certain magnetic field and temperature ranges. A magnetic skyrmion is a topological configuration in which local spins wrap around the unit sphere for an integer number of times.  Skyrmions, first proposed for particle physics decades earlier, have recently been observed in a series of non-centrosymmetric helimagnets in condensed matter physics by neutron scattering or transmission electron microscopy. Skyrmions show various novel properties inherent to its topological nature, such as topological Hall effect, topological stability, and ultralow critical current for movement, which offer the skyrmion promising prospects for next generation spintronic devices and information storages. 

  In this talk, I will show the intimate connection between the skyrmion’s nontrivial topology and distinguished symmetries, which leads to many other novel properties of helimagnets. The skyrmion dynamics under electric current or temperature gradient will be discussed, and several routes to individual skyrmions will be presented. Finally I will introduce a new skyrmion material with rich parent phases.