Temperature-dependent electronic structure in a higher-order topological insulator candidate Eu In 2 As 2

Higher-order topological insulators (HOTIs) have enticed enormous research interests owing to their novelty in supporting gapless states along the hinges of a crystal. Despite several theoretical predictions, enough experimental confirmation of the HOTI state in crystalline solids is still lacking. It is shown that interplay between topology and magnetism can give rise to various magnetic topological states, including HOTI and axion insulator states. Here, using high-resolution angle-resolved photoemission spectroscopy combined with the first-principles calculations, we report a systematic study of the electronic structure and its evolution across the magnetic phase transition in ${\mathrm{EuIn}}_{2}{\mathrm{As}}_{2}$ which possesses an antiferromagnetic ground state below 16 K. Antiferromagnetic ${\mathrm{EuIn}}_{2}{\mathrm{As}}_{2}$ has been predicted to host both the axion insulator and the HOTI states. We directly observe the linearly dispersing holelike bands crossing the Fermi level and the change in their dispersion across the magnetic phase transition. Our paper points to ${\mathrm{EuIn}}_{2}{\mathrm{As}}_{2}$ as being a promising material for the exploration of interplay between topology and magnetism.