2016/08/31 by Tao Hong, Y. Qiu, M. Matsumoto +7 · 1 citation
Physics and Astronomy · #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1038/ncomms15148
published as Nat. Commun. 8, 15148 (2017) · 8 pages, 6 figures, some typos were corrected in the revised version
arxiv created 2017/05/05 · arxiv updated 2017/05/24
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.