Topological or not? ARPES reveals topologically non-trivial electronic structure in single crystals of the ferrimagnetic-TI candidate Mn(1+x)Sb(2-x)Te4.

The combination of nontrivial band topology with magnetism results in a wide variety of exotic electronic phases that - if realized at high temperatures - could revolutionize fields like spintronics or low-power consumption electronics. The new, second-generation ferrimagnetic (fM) compound Mn_1+xSb_2-xTe₄ (0.1 ≤ x ≤ 1, abbreviated here as MST) promises to host the quantum anomalous Hall effect (QAHE) and other topological phases at higher temperatures than any of its predecessors, with T_C up to 73K. The long-range magnetic order of these MST single crystals is confirmed, therefore the big question is “are they topologically non-trivial?”. I present temperature-dependent ARPES measurements that clearly argue that the answer is “yes”. Aditionally, I will discuss further temperature dependent features in the banstructure that could suggest the potential importance of electron-magnon coupling in understanding the ARPES data.