Discovery of topological phase transitions opened one of the most fruitful area in solid state physics and chemistry. Topologically non-trivial matter is presented by 2D and 3D topological insulators, Dirac and Weyl semimetals and others. They differ from “normal” materials by peculiar electrons behavior, that can be quantified via so-called Chern numbers. 

Recently it was shown that meeting of non-trivial topology with magnetism results in novel phases of matter, such as Quantum Anomalous Hall phase and Majorana zero modes. The first intrinsic magnetic topological insulator (IMTI) MnB2Te4 became the most promising candidate for these phenomena observation.[1] Here, recent experimental results on the IMTI-family materials will be shown and discussed. The main tool used for studying the electronic and spin structure was the state-of-the-art angle-resolved photoelectron spectroscopy. 

We have demonstrated that by means of superlattice (MnB2Te4) (Bi2Te3)m construction  where m is 0..6 it is possible to control the exchange interaction and topological surface states localization. On the other hand, our data have revealed the magnetic properties tuning and topological phase transitions of MnBi2Te4 via Ge, Pb and  Sn atoms doping. Furthermore, intriguing interface effects have been observed in heterostructures of MBT with superconducting Pb and 2D topological Bi ultrathin films.[2]

On the other hand, non-trivial topology and magnetism can be induced in graphene, contacted with heavy and magnetic atoms. Our recent observations of non-trivial topology and sublattice ferrimagnetism in graphene on metallic and semiconducting substrates with various metal atoms intercalation will be discussed.[3] 

Fig.1 DFT edge states electron density of 1 BL Bi/MBT system. Inset: ARPES data for MnBi2Te4 clean surface and 1 Bl Bi/MnBi2Te4 interface

 

[1] Otrokov, M. M., Klimovskikh, et al., Nature, 576(7787), 416-422. (2019)

[2] Klimovskikh I.I. et al., , J. Phys. Chem. Lett. 13, 29, 6628–6634  (2022)

[3] Rybkin A.G. et al., Phys. Rev. Lett, 129, 226401 (2022)

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https://us06web.zoom.us/j/5081440931

Meeting ID: 508 144 0931

Seminar hosts: Neven Šantić i Matija Čulo