Evidence for magnon-phonon coupling in the topological magnet Cu$_3$TeO$_6$

Song Bao; Zhengwei Cai; Wenda 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

doi:10.1103/physrevb.101.214419

arXiv · 2006.07012

Evidence for magnon-phonon coupling in the topological magnet Cu$_3$TeO$_6$

Song Bao·Zhengwei Cai·Wenda 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

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Abstract

We perform thermodynamic and inelastic neutron scattering (INS) measurements to study the lattice dynamics (phonons) of a cubic collinear antiferromagnet Cu$_3$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\'{e}el 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, which is new 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 Cu$_3$TeO$_6$.

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Song Bao, Zhengwei Cai, Wenda 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. 2020-06-12. Evidence for magnon-phonon coupling in the topological magnet Cu$_3$TeO$_6$. https://doi.org/10.1103/physrevb.101.214419

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