Evidence for magnon-phonon coupling in the topological magnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Cu</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>TeO</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:mrow></mml:math>
Song Bao, Zhengwei Cai, W. Si, Wei Wang, Xiaomeng Wang, Yanyan Shangguan, Zhen Ma, Zhao-Yang Dong, Ryoichi Kajimoto, Kazuhiko Ikeuchi, Shun-Li Yu, Jian Sun, Jian‐Xin Li, Jinsheng Wen
Abstract
We perform thermodynamic and inelastic neutron scattering (INS) measurements to study the lattice dynamics (phonons) of a cubic collinear antiferromagnet ${\mathrm{Cu}}_{3}{\mathrm{TeO}}_{6}$ which hosts topological spin excitations (magnons). While the specific heat and thermal conductivity results show that the thermal transport is dominated by phonons, the deviation of the thermal conductivity from a pure phononic model indicates that there is a strong coupling between magnons and phonons. In the INS measurements, we find a mode in the excitation spectra at 4.5 K, which exhibits a slight downward dispersion around the Brillouin zone center. This mode disappears above the N\'eel temperature and thus cannot be a phonon. Furthermore, the dispersion is distinct from that of a magnon. Instead, it can be explained by the magnon-polaron mode, collective excitations resulting from the hybridization between magnons and phonons. We consider the suppression of the thermal conductivity and emergence of the magnon-polaron mode to be evidence for magnon-phonon coupling in ${\mathrm{Cu}}_{3}{\mathrm{TeO}}_{6}$.