Abstract
We present single-crystal neutron scattering measurements of the spin- equilateral triangular-lattice antiferromagnet . Besides confirming that the magnetic moments lie in the plane for zero magnetic field and then determining all the exchange parameters of the minimal quasi-2D spin Hamiltonian, we provide conclusive experimental evidence of magnon decay through observation of intrinsic line broadening. Through detailed comparisons with the linear and nonlinear spin-wave theories, we also point out that the large- approximation, which is conventionally employed to predict magnon decay in noncollinear magnets, is inadequate to explain our experimental observation. Thus, our results call for a new theoretical framework for describing excitation spectra in low-dimensional frustrated magnets under strong quantum effects.
- Received 18 July 2015
DOI:https://doi.org/10.1103/PhysRevLett.116.087201
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