Abstract
An inelastic neutron scattering study of (, Br) shows strong dispersive modes with large energy gaps persisting far above , notably in . The anomalous features: a coexisting unusually weak Goldstone-like mode observed in and the size of the energy gaps cannot be explained by existing theories, such as our mean-field or random-phase approximation. We argue that our findings represent a new general type of behavior due to intercluster quantum fluctuations and call for development of a new theoretical approach.
- Received 28 October 2008
DOI:https://doi.org/10.1103/PhysRevLett.102.177202
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