Spin quenching and transport by hidden Dzyaloshinskii-Moriya interactions

Explicit interactions, 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 uniaxial antiferromagnets, a hidden Dzyaloshinskii-Moriya interaction with retaining global inversion symmetry quenches the spin of the magnon along the N\'eel vector $\mathbf{n}$, thus forbidding its angular-momentum flow. Some magnon spins, termed ``nodal'' and ``corner'' spins, survive when they distribute 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 $\mathbf{n}$ 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.