2026/07/20 by Dingbin Huang, Jonathon Kruppe, Resham Babu Regmi +3
#cond-mat.str-el #cond-mat.mtrl-sci
Manganese telluride (MnTe) has recently emerged as a prototypical g-wave altermagnet, providing an ideal platform to investigate the non-equilibrium excitations of altermagnetic order. Here, we report simultaneous spatial mapping of the local equilibrium orientation of the Néel vector, φL(r), alongside the amplitude, Δφ(r,t), and frequency, Ω(r), of photoexcited spin waves. Based on these measurements, we place a remarkably low upper bound of ≈ 60~μeV (0.7 K) on the spin-wave gap arising from intrinsic anisotropy. This exceptionally weak hexagonal anisotropy (K6) renders the altermagnetic order highly susceptible to optical tuning, allowing coherent spin waves to be driven by a photoinduced enhancement of K6. Above a threshold pump fluence, our spatial maps reveal that this photomodulation manifests as a six-fold symmetric sawtooth dependence of Δφ on φL and a cycloid-like modulation of Ω. Ultimately, the near-isotropy of the Néel vector in MnTe enables optical and mechanical control over the orientation of spin-splitting in the electronic band structure, offering new pathways for altermagnetic spintronics.