Manipulating the topological state with magnetic field: magneto-optical study of magnetic topological materials

Master's thesis

Magnetic topological materials, Magneto-optical spectroscopy

Magnetic Topological Materials

In recent years, the discovery of magnetic topological materials has made the interaction between magnetism and topological state a hot topic. Co3Sn2S2 [1] and EuCd2As2 [2] are two representative magnetic topological materials and their topological states are greatly affected by the magnetic moments. Theoretical investigations pointed out that in addition to the magnitude of magnetic moments, the orientation also affects the topological state [2, 3]. Although the magnetic moments in these two materials have easy axis characteristics, their orientation can be manipulated by external magnetic field.

Optical spectroscopy can measure materials’ joint density of states [4], indirectly providing the information of band structure as well as topology. In this project, we are going to use the in-situ magnetic field to tune the magnetic moments’ orientation and simultaneously measure the optical response. Through the analysis of magneto-optical spectroscopy, we can have a deeper understanding of the interaction between magnetism and topology and important information for future applications of these materials.

a) and b) are different spin textures of EuCd2As2, c) and d) are the corresponding topologial states. e) shows the predictred optical conductivities.

References:

  1. Liu, E. et al. Giant anomalous Hall effect in a ferromagnetic Kagome-lattice semimetal. Nat Phys 14, 1125-1131 (2018).
  2. Ma, J. Z. et al. Spin fluctuation induced Weyl semimetal state in the paramagnetic phase of EuCd2As2. Science advances 5, eaaw4718 (2019).
  3. Akihiro Ozawa et al. Two-Orbital Effective Model for Magnetic Weyl Semimetal in Kagome-Lattice Shandite. J. Phys. Soc. Jpn. 88, 123703 (2019)
  4. Dressel and G. Grüner, Electrodynamics of Solids (Cambridge University Press, Cambridge, England, 2002).
This image shows Run Yang

Run Yang

Dr.

Fellow of the Alexander von Humboldt Foundation

This image shows Martin Dressel

Martin Dressel

Prof. Dr. rer. nat.

Head of Institute

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