Abstract
We predict that spin waves in an ordered quantum antiferromagnet in a strong magnetic field become unstable with respect to spontaneous two-magnon decays. At zero temperature, the instability occurs between the threshold field and the saturation field . As an example, we investigate the high-field dynamics of a Heisenberg antiferromagnet on a square lattice and show that the single-magnon branch of the spectrum disappears in most of the Brillouin zone.
- Received 10 August 1998
DOI:https://doi.org/10.1103/PhysRevLett.82.4536
©1999 American Physical Society