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arXiv · 2002.06283

Low energy magnons in the chiral ferrimagnet $\text{Cu}_2\text{OSeO}_3$: a coarse-grained approach

Yi Luo·G. G. Marcus·B. A. Trump·J. Kindervater·M. B. Stone·J. A. Rodriguez-Rivera·Yiming Qiu·T. M. McQueen·O. Tchernyshyov·C. Broholm
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Abstract

We report a comprehensive neutron scattering study of low energy magnetic excitations in the breathing pyrochlore helimagnetic $\text{Cu}_2\text{OSeO}_3$. Fully documenting the four lowest energy magnetic modes that leave the ferrimagnetic configuration of the "strong tetrahedra" intact ($|\hbar\omega|<13$ meV), we find gapless quadratic dispersion at the $\Gamma$ point for energies above 0.2 meV, two doublets separated by 1.6(2) meV at the $R$ point, and a bounded continuum at the $X$ point. Our constrained rigid spin cluster model relates these features to Dzyaloshinskii-Moriya (DM) interactions and the incommensurate helical ground state. Combining conventional spin wave theory with a spin cluster form-factor accurately reproduces the measured equal time structure factor through multiple Brillouin zones. An effective spin Hamiltonian describing the complex anisotropic inter-cluster interactions is obtained.

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Yi Luo, G. G. Marcus, B. A. Trump, J. Kindervater, M. B. Stone, J. A. Rodriguez-Rivera, Yiming Qiu, T. M. McQueen, O. Tchernyshyov, C. Broholm. 2020-02-14. Low energy magnons in the chiral ferrimagnet $\text{Cu}_2\text{OSeO}_3$: a coarse-grained approach. https://doi.org/10.1103/physrevb.101.144411

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