In this work, we employed angle resolved photoemission spectroscopy (ARPES) to analyze the temperature dependent changes in the electronic structure of the first antiferromagnetic topological insulator MnBi₂Te₄ upon crossing the Néel temperature T_N ≈ 25 K. We observed an exchange splitting of the bulk conduction band, which has a power law dependence on temperature (1−T/T₀)^2β with an onset temperature T₀ well matching the measured bulk T_N. We found a matching temperature evolution of the topological surface states integrated spectral weight in the vicinity of the Dirac point. Furthermore, we observed an additional quasi-2D state with Rashba-type splitting, which is also affected by the emerged magnetism and exhibits an opening of a gap, reminiscent of the effect of an out-of-plane magnetic field, below T_N. All these findings point toward strong evidence of the interplay between emerged magnetism with bulk and topological surface states. The observed temperature-dependent effects in MnBi₂Te₄ may be used as an experimental fingerprint for the presence of magnetism and may guide the future analysis of ARPES spectra in magnetic topological insulators.

“Signatures of temperature driven antiferromagnetic transition in the electronic structure of topological insulator MnBi2Te4” D. A. Estyunin, I. I. Klimovskikh, A. M. Shikin, E. F. Schwier, M. M. Otrokov, A. Kimura, S. Kumar, S. O. Filnov, Z. S. Aliev, M. B. Babanly and E. V. Chulkov. Cite as: APL Mater. 8, 021105 (2020); doi: 10.1063/1.5142846