Anomalously large damping of long-wavelength quasiparticles caused by long-range interaction
Abstract
We demonstrate that long-range interaction in a system can lead to a very strong interaction between long-wavelength quasiparticles and make them heavily damped. In particular, we discuss magnon spectrum using 1/S expansion in 3D Heisenberg ferromagnet (FM) with arbitrary small dipolar forces at T<<T_C. We obtain that a fraction of long-wavelength magnons with energies e_k<T has anomalously large damping G_k (ratio G_k/e_k reaches 0.3 for certain k). This effect is observed both in quantum and classical FMs. Remarkably, this result contradicts expectation of the quasiparticle concept according which a weakly excited state of a many-body system can be represented as a collection of weakly interacting elementary excitations. Particular materials are pointed out which are suitable for corresponding experiments.
Keywords
Cite
@article{arxiv.1007.3081,
title = {Anomalously large damping of long-wavelength quasiparticles caused by long-range interaction},
author = {A. V. Syromyatnikov},
journal= {arXiv preprint arXiv:1007.3081},
year = {2010}
}
Comments
13 pages, 6 figures, some minor corrections have been made, to appear in PRB