2016/12/31 by Akashdeep Kamra, Utkarsh Agrawal, Wolfgang Belzig · 1 citation
Physics and Astronomy · #cond-mat.mes-hall #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevb.96.020411
published as Phys. Rev. B 96, 020411 (2017) · 5 pages, 3 figures, Supplementary material
arxiv created 2017/07/22 · arxiv updated 2017/07/26
Interactions are responsible for intriguing physics, e.g. emergence of exotic ground states and excitations, in a wide range of systems. Here we theoretically demonstrate that dipole-dipole interaction leads to bosonic eigen-excitations with average spin ranging from zero to above ℏ in magnets with uniformly magnetized ground states. These exotic excitations can be interpreted as quantum coherent conglomerates of spin ℏ magnons, the eigen-excitations 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 ± ℏ magnons. The latter re-emerge when the symmetry is broken by a sufficiently large applied magnetic field. The average spin greater than ℏ is accompanied by vacuum fluctuations and may be considered to be a weak form of frustration.