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Skyrmions, which are representative of topological magnetism, have been studied intensively around the world since the successful direct observation of them in 2009. One of the reasons for the present interest in Skyrmions is that they are robust against perturbations owing to their nontrivial topology of spin configuration and are expected to lead to the development of magnetic storage devices with ultra-high density and ultra-low power consumption. On the other hand, in most studies on Skyrmions over the past decade, spins have been treated classically.

In such a trend, we studied topological magnetism in spin-1 quantum magnets. Using homotopy analysis and a numerical optimization technique, we have discovered a new type of Skyrmions (solitons) with emergent interactions in the S=1 bilinear biquadratic (BBQ) model on a triangular lattice at a global SU(3) symmetric point [1]. Recently, through interdisciplinary collaboration, we introduced a generalized Dzyaloshinskii- Moriya (DM) interaction to the S=1 BBQ model and constructed a stable isolated generalized (CP²) Skyrmion solution analytically [2]. By further investigation, we have also numerically found that generalized (CP²) Skyrmion crystals are stabilized as the ground state in S=1 quantum magnets with the generalized DM interaction [3].

The generalized Skyrmions show a nontrivial structure of not only dipole moments but also quadrupole moments and thus have no counterpart in the classical spin systems. In this seminar, we will discuss these generalized Skyrmions in detail.

[1] H. T. Ueda, Y. Akagi, and N. Shannon, Phys. Rev. A. 93, 021606(R) (2016).
[2] Y. Akagi, Y. Amari, N. Sawado, and Y. Shnir, Phys. Rev. D 103, 065008 (2021).
[3] Y. Amari, Y. Akagi, S. Gudnason, M. Nitta, Y. Shnir, Phys. Rev. B 106, L100406 (2022).

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