MnTe has recently attracted exceptional attention due to its well-established altermagnetism, prompting a thorough reexamination of its properties. In particular, it was found that a Raman-active excitation at $\sim 175{\mathrm{cm}}^{-1}$, routinely assigned to the $E_{2g}$ phonon, is incompatible with this interpretation. It was further hypothesized that this mode is a “leakage,” due to symmetry lowering, of an otherwise forbidden phonon. Here, using first-principles calculations, we decisively rule out this hypothesis and propose an alternative interpretation that the “mystery mode” is an electronic excitation, i.e., a plasmon, enabled by hole self-doping. The resolution of this mystery will require additional experiments and could shed new light on the nature of electronic transport in MnTe.

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• Phonons
• Altermagnets
• Density functional calculations
• First-principles calculations
• Raman spectroscopy