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Topological spin textures, such as two-dimensional skyrmion lattices (SkLs) and three-dimensional hedgehog lattices (HLs) are approximately represented by superpositions of multiple spin density waves, and hence, called multiple-Q spin textures. In such spin structures, the phase degree of freedom of the superposed waves plays an important role in the topological properties as well as the symmetry of the magnetic textures, but the systematic investigation has not been performed thus far. In this study, we theoretically investigate the evolution of magnetic and topological properties in SkLs composed of three spin density waves (3Q-SkL) and HLs composed of four spin density waves (4Q-HL) while changing the phases as well as the magnetization. By introducing a hyperspace to deal with the phases systematically, we find that the 3Q-SkLs change their skyrmion number among -2, -1, 0, 1, and 2 depending on the phase and magnetization. In the case of the 4Q-HLs, we clarify that the density and configuration of topological objects called hedgehogs and antihedgehogs change in a wide range. Our results provide good references to discuss how the actual systems experience the magnetic and topological transitions in an applied magnetic field.

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Kotaro Shimuzu, The University of Tokyo
Seminar Room 0.03, ETP and zoom (https://uni-koeln.zoom.us/j/92165384988 )
Contact: Simon Trebst