Kink in the electronic structure of MnSb2Te4 : Band feature or electron-magnon coupling?

MnSb2Te4 is a promising magnetic topological insulator candidate, composed of septuple layers stacked along the c-axis with van der Waals gaps in between. The Mn2+ ions order ferrimagnetically at 32 K. Currently, there is only one published INS study from Oak Ridge that measured low-energy magnons (0-20 meV) in a powder sample.

Our group has conducted several experimental studies using angle-resolved photoemission spectroscopy (ARPES) on MnSb2Te4 single crystals with TC = 32 K. Our data not only supports the existence of nontrivial topology but also reveals for the first time a strong coupling between the magnetic ground state and the topological surface states. Such strong coupling is unprecedented in the literature on magnetic topological materials and could be explained by considering the role of magnon-mediated interactions in the electronic structure. However, this coupling is observed at a higher energy scale (~150 meV), and the lack of INS data in this range prevents us from unambiguously linking the observed features to electron-magnon coupling.

We would like to perform a quick screening measurement on a ~6 g powder sample of MnSb2Te4 using INS, ideally covering the 0 200 meV energy range at one temperature T < 32 K. Our main goal is to look for any signal of magnons in the ~150 meV region that could support the ARPES observations and help distinguish whether the kink we observe is a signature of magnon-mediated interactions.