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  • Title: Nature of the Dirac gap modulation and surface magnetic interaction in axion antiferromagnetic topological insulator [Formula: see text].
    Author: Shikin AM, Estyunin DA, Klimovskikh II, Filnov SO, Schwier EF, Kumar S, Miyamoto K, Okuda T, Kimura A, Kuroda K, Yaji K, Shin S, Takeda Y, Saitoh Y, Aliev ZS, Mamedov NT, Amiraslanov IR, Babanly MB, Otrokov MM, Eremeev SV, Chulkov EV.
    Journal: Sci Rep; 2020 Aug 06; 10(1):13226. PubMed ID: 32764583.
    Abstract:
    Modification of the gap at the Dirac point (DP) in axion antiferromagnetic topological insulator [Formula: see text] and its electronic and spin structure have been studied by angle- and spin-resolved photoemission spectroscopy (ARPES) under laser excitation at various temperatures (9-35 K), light polarizations and photon energies. We have distinguished both large (60-70 meV) and reduced ([Formula: see text]) gaps at the DP in the ARPES dispersions, which remain open above the Neél temperature ([Formula: see text]). We propose that the gap above [Formula: see text] remains open due to a short-range magnetic field generated by chiral spin fluctuations. Spin-resolved ARPES, XMCD and circular dichroism ARPES measurements show a surface ferromagnetic ordering for the "large gap" sample and apparently significantly reduced effective magnetic moment for the "reduced gap" sample. These observations can be explained by a shift of the Dirac cone (DC) state localization towards the second Mn layer due to structural disturbance and surface relaxation effects, where DC state is influenced by compensated opposite magnetic moments. As we have shown by means of ab-initio calculations surface structural modification can result in a significant modulation of the DP gap.
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