Abstract
Interactions are responsible for intriguing physics, e.g., the emergence of exotic ground states and excitations, in a wide range of systems. Here, we theoretically demonstrate that dipole-dipole interactions lead to bosonic eigenexcitations with average spin ranging from zero to above in magnets with uniformly magnetized ground states. These exotic excitations can be interpreted as quantum coherent conglomerates of spin magnons, the eigenexcitations when the dipolar interactions are disregarded. We further find that the eigenmodes in an easy-axis antiferromagnet are spin-zero quasiparticles instead of the widely believed spin magnons. The latter reemerge when the symmetry is broken by a sufficiently large applied magnetic field. The average spin greater than is accompanied by vacuum fluctuations and may be considered to be a weak form of frustration.
- Received 13 December 2016
DOI:https://doi.org/10.1103/PhysRevB.96.020411
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