Angle-Resolved Photoemission of Topological Matter: Examples from Magnetism, Electron Correlation, and Phase Transitions

Topological materials promise new functionalities, which are revealed with the help of angle-resolved photoemission. Herein, the search for the magnetic bandgap at the Dirac point as a precondition for the quantum anomalous Hall effect is reviewed and its opening for the topological insulator heterostructure MnBi2Te4/Bi2Te3 is demonstrated. Essential preconditions are explained and the reasons why nonmagnetic gaps occur when Se replaces Te. Angle-resolved photoelectron spectroscopy (ARPES) probes the quantum mechanical final state, and this allows investigation of spin manipulation by light using spin-resolved ARPES and the dependence of the charge carrier lifetime on the peculiar spin texture of topological states. It is shown that ARPES data do not support SmB6 as the first strongly correlated topological insulator and an alternative, trivial explanation for the results of ARPES and electrical transport experiments is formulated. Epitaxially grown topological crystalline insulators are, due to their dependence on crystal symmetries, more versatile in the control of individual bulk band inversions. It is shown that this leads to topological quantum phase transitions and associated novel functionalities. Finally, the surface and bulk band connectivity of a type-II 3D Weyl semimetal is investigated and an outlook is given for the scientific field.

Automated summary

This paper reviews the search for magnetic bandgap in topological materials and demonstrates the opening of a magnetic bandgap in the topological insulator heterostructure MnBi2Te4/Bi2Te3. It discusses the reasons for nonmagnetic gaps when Se replaces Te, introduces the use of ARPES to probe the quantum final state, and highlights the importance of studying spin texture in topological states.