Two-dimensional Ferromagnetic Extension of a Topological Insulator

日時　2022年7月11日　（月）　16：50～17：50
場所　広島大学放射光科学研究センター　2階　セミナー室(オンライン併用)
講師　Philipp Kagerer
(University of Würzburg, Department for experimental Physics VII)

As a promising host-system for novel spintronic applications, magnetic topological insulators (TI, MTI’s) hosting quantized and spin-polarized transport properties are a highly intriguing research topic. Over the recent years, many design approaches, ranging from magnetic surface coverage over dilute bulk doping up to the use of intrinsic magnetic structures have been tried experimentally, where the key challenge has always been a compromise between strong magnetic order and high crystalline quality [1]. In our work we present the experimental realisation of a novel design approach by magnetically extending only the surface of a 3D TI with a 2D layered magnet within the same symmetry class. The magnetic extension approach [2], built up out of the material combination Bi₂Te₃ and MnBi₂Te₄ [3,4] enables a direct interaction between the topological surface state (TSS) density of states and the magnetically active Mn ions, leading to a clear signature of time reversal symmetry breaking while maintaining a highly ordered system.

I will introduce the field of magnetic topological insulators from a fundamental point of view up to the current state of research on this topic and subsequently present our results on the electronic structure and magnetic properties of the MnBi₂Te₄ – Bi₂Te₃ heterostructure system, grown by molecular beam epitaxy (MBE). This will combine a thorough study of the 2-dimensional magnetism by X-ray magnetic circular dichroism (XMCD) and magnetotransport is this system with results from high-resolution photoemission experiments showing the clear interaction between the surface magnetic order and the topological surface state.

[1] K.M. Fijalkowski et al., Nature Commun. 12, 5599 (2021).
[2] M.M. Otrokov et al., JETP Lett. 105, 297-302 (2017).
[3] M.M. Otrokov et al., Nature, 576, pages 416–422 (2019).
[4] P. Kagerer et al., J. Appl. Phys. 128, 135303 (2020).

問合せ先　出田真一郎（放射光科学研究センター）