Pantheon SEMPARIS Le serveur des séminaires parisiens Paris

Status Confirmed
Seminar Series SEM-LPTMC
Subjects cond-mat.mes-hall
Date Monday 12 February 2018
Time 10:45
Institute LPTMC
Seminar Room tower 13-12 5th floor room 5-23
Speaker's Last Name Thiaville
Speaker's First Name André
Speaker's Email Address thiaville [at] lps [dot] u-psud [dot] fr
Speaker's Institution LPS Orsay
Title Topology in Magnetism
Abstract After recalling what topology is, the seminal work by Ernst Feldtkeller [1] introducing topology in magnetism will be described. His arguments were generalized and systematized, first by Maurice Kléman and coworkers [2], into what is now known as the topological theory of defects, for all types of order parameter and samples’ dimensionality and topology [3]. The tools of this theory can be also used to define topologically stable continuous magnetic structures, also called topological solitons, prominent examples being the vortex and the skyrmion. The associated topological number will be recalled and its signification discussed through examples. The distinct role of chirality, compared to topology, will be stressed. We shall then describe the links of topology with magnetization dynamics. The electrical transport through magnetic textures with non-trivial topology will also be discussed. Finally, the energy cost of “breaking the topology” will be discussed, through the following questions: what is the energy of the singular Bloch point, how large is the energy barrier to reverse a vortex or to delete a magnetic skyrmion ? [1] E. Feldtkeller, Mikromagnetisch stetige und unstetige Magnetisierungskonfigurationen, Z. angew. Phys. 19, 530-536 (1965). English translation IEEE Trans. Magn. 53, 0700308 (2017). [2] G. Toulouse, M. Kléman, Principles of a classification of defects in ordered media, J. Physique Lett. 37, L149-151 (1976). [3] N.D. Mermin, The topological theory of defects in ordered media, Rev. Mod. Phys. 51, 591-648 (1979); M. Kléman, Points, lines and walls (Wiley, New York, 1983).
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