The notion of a quasiparticle, such as a phonon, a roton, or a magnon, is used in modern condensed matter physics to describe an elementary collective excitation. The intrinsic zero-temperature magnon damping in quantum spin systems can be driven by the interaction of the one-magnon states and multi-magnon continuum. However, detailed experimental studies on this quantum many-body effect induced by an applied magnetic field are rare. Here we present a high-resolution neutron scattering study in high fields on an S=1/2 antiferromagnet C9H18N2CuBr4. Compared with the non-interacting linear spin-wave theory, our results demonstrate a variety of phenomena including field-induced renormalization of one-magnon dispersion, spontaneous magnon decay observed via intrinsic linewidth broadening, unusual non-Lorentzian two-peak structure in the excitation spectra, and a dramatic shift of spectral weight from one-magnon state to the two-magnon continuum.
@article{arxiv.1608.08172,
title = {Field induced spontaneous quasiparticle decay and renormalization of quasiparticle dispersion in a quantum antiferromagnet},
author = {Tao Hong and Y. Qiu and M. Matsumoto and D. A. Tennant and K. Coester and K. P. Schmidt and F. F. Awwadi and M. M. Turnbull and H. Agrawal and A. L. Chernyshev},
journal= {arXiv preprint arXiv:1608.08172},
year = {2017}
}
Comments
8 pages, 6 figures, some typos were corrected in the revised version