Spin Quenching and Transport by Hidden Dzyaloshinskii-Moriya Interactions

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