Search

The layered van der Waals antiferromagnet MnBi$_2$Te$_4$ has been predicted to combine the band ordering of archetypical topological insulators such as Bi$_2$Te$_3$ with the magnetism of Mn, making this material a viable candidate for the realization of various magnetic topological states. We have systematically investigated the surface electronic structure of MnBi$_2$Te$_4$(0001) single crystals by use of spin- and angle-resolved photoelectron spectroscopy experiments. In line with theoretical predictions, the results reveal a surface state in the bulk band gap and they provide evidence for the influence of exchange interaction and spin-orbit coupling on the surface electronic structure., Revised version

Kondo insulator $\mathrm{Sm}{\mathrm{B}}_{6}$ has attracted attention because it can realize new topological phenomena driven by the interplay between strong correlation effect and topology. However, its topological nature is still under debate. To examine the topological aspect, we demonstrate the nonmagnetic La and magnetic Ce doping dependence of the resistance of $\mathrm{Sm}{\mathrm{B}}_{6}$. Moreover, the resistance ratios of different thicknesses are analyzed to confirm the surface contribution. Lightly doped La samples show a purely conducting surface region at low temperature, whereas the lightly doped Ce samples do not have any conducting region at low temperature. Furthermore, based on the analysis of the electrical transport data of $\mathrm{S}{\mathrm{m}}_{1\ensuremath{-}x}\mathrm{L}{\mathrm{a}}_{x}{\mathrm{B}}_{6}$ $(0.0\ensuremath{\le}x\ensuremath{\le}1.0)$, an electronic phase diagram was found, composed of four regions: region I $(0.0\ensuremath{\le}x\ensuremath{\le}0.06)$, II $(0.1\ensuremath{\le}x\ensuremath{\le}0.15)$, III $(x\ensuremath{\approx}0.2)$, and IV $(0.25\ensuremath{\le}x\ensuremath{\le}1.0)$. Region I is characterized by the presence of conducting surface states, region II is characterized by the insulating phase due to the $d\ensuremath{-}f$ hybridization gap without the conducting surface state, region III is characterized by the disappearance of the $d\ensuremath{-}f$ hybridization gap and the existence of valence fluctuation, and region IV is a typical metallic state.

Using angle-resolved photoelectron spectroscopy we investigate the surface electronic structure of the three-dimensional topological insulator (TI) Sb${}_{2}$Te${}_{3}$(0001). Our data show the presence of a topological surface state in the bulk energy gap with the Dirac point located above the Fermi level. The adsorption of Cs atoms on Sb${}_{2}$Te${}_{3}$(0001) gives rise to a downward energy shift of the electronic valence band states which saturates at a value of $\ensuremath{\sim}$200 meV. For the saturation coverage the Dirac point of the linearly dispersive surface state resides in close proximity to the Fermi level. The electronic structure of the Cs/Sb${}_{2}$Te${}_{3}$ interface therefore considerably deviates from previously studied metal-TI interfaces based on the isostructural compound Bi${}_{2}$Se${}_{3}$ which points to the importance of atomic composition in these hetero systems.