Spin Quenching and Transport by Hidden Dzyaloshinskii-Moriya Interactions

Explicit interactions, \textit{e.g.}, dipolar and exchange couplings, usually govern magnetization dynamics. Some interactions may be hidden from the global crystal symmetry. We report that in a large class of \textit{uniaxial} antiferromagnets, a \textit{hidden} Dzyaloshinskii-Moriya interaction with retaining global inversion symmetry quenches the spin of magnon along the N\'eel vector ${\bf n}$, thus forbidding its angular-momentum flow. Some magnon spins, termed ``nodal" and ``corner" spins, survive when they distribute \textit{singularly} at the hot spots, i.e., high-symmetric degeneracy points in the Brillouin zone, and are protected by crystal symmetries. The biased magnetic field along ${\bf n}$ broadens such distributions, allowing bulk spin transport with unique signatures in the magnetic field and temperature dependencies. This explains recent experiments and highlights the role of hidden interaction.