Abstract
Using a variational method, we derive an exact upper bound for one-magnon excitation energy in ferromagnetic spinor gases, which limits the quantum corrections to the effective mass of a magnon to be positive. We also derive an upper bound for one-magnon excitation energy in lattice systems. The results hold for both Bose and Fermi systems in dimensions as long as the interaction is local and invariant under spin rotation.
- Received 13 March 2015
DOI:https://doi.org/10.1103/PhysRevA.91.043624
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