Skyrmionic matters: Multidimensional solitons in chiral magnetism and their extended topological textures

Date

May 10, 2012

Time

2:00 PM - 3:00 PM

Speaker

Ulrich K. Rössler

Affiliation

IFW Dresden

Language

en

Main Topic

Physik

Other Topics

Physik

Host

Condensed Matter Seminar

Description

In non-centrosymmetric magnets the chiral Dzyaloshinskii-Moriya (DM) interactions stabilize two-dimensional topological solitons. These Skyrmions are smooth, i.e. defect free, and static [1]. The phenomenological continuum theory of these states can be cast in the form of Ginzburg-Landau-functionals with Lifshitz invariants revealing a fixed gauge-background as the origin for these exceptional multi-dimensionally localized states. Extended chiral Skyrmionic states can exist in many magnetic systems as condensed mesophases formed from such solitonic units [2], because the DM-couplings are the leading spin-orbit effect, if allowed by acentric crystal symmetry or induced by broken inversion symmetry at surfaces. The stability of such skyrmion matter states is determined by the particle-like nature of the Skymion core and a geometrical frustration that prevents a homogeneous space-filling arrangement of double-twist structures. These states are determined by short-range magnetic exchange couplings and are fundamentally different from the known classical bubbles, i.e. cylindrical magnetic domains stabilized by dipolar stray field energies [3]. As single objects, they can be as small as a few lattice spacings, if the DM-exchange is exceptionally strong. Currently, there is a surge of experimental observations of chiral textures in non-centrosymmetric magnetic systems. Within the framework of phenomenological models, the occurrence of isolated and condensed Skyrmions can be understood and will be set in relation to these experimental data: known facts about these structures, novel ideas about the magnetic precursors and the thermal ordering transition in these systems, and future directions in this new research field will be discussed. [1] A.N. Bogdanov, D.A. Yablonskii, JETP 68 (1989) 101. [2] U.K. Rößler, A.N. Bogdanov, C. Pfleiderer, Nature 442 (2006) 797. [3] N. S. Kiselev, A. N. Bogdanov, R. Schäfer, U. K. Rößler, Phys. Rev. Lett. 107 (2011) 179701.

Last modified: May 10, 2012, 9:37:04 AM