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arXiv · 1907.02061

Dirac magnons in a honeycomb lattice quantum XY magnet CoTiO3

Bo Yuan·Ilia Khait·Guo-Jiun Shu·F. C. Chou·M. B. Stone·J. P. Clancy·Arun Paramekanti·Young-June Kim
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Abstract

The discovery of massless Dirac electrons in graphene and topological Dirac-Weyl materials has prompted a broad search for bosonic analogues of such Dirac particles. Recent experiments have found evidence for Dirac magnons above an Ising-like ferromagnetic ground state in a two-dimensional (2D) kagome lattice magnet and in the van der Waals layered honeycomb crystal CrI$_3$, and in a 3D Heisenberg magnet Cu$_3$TeO$_6$. Here we report on our inelastic neutron scattering investigation on large single crystals of a stacked honeycomb lattice magnet CoTiO$_3$, which is part of a broad family of ilmenite materials. The magnetically ordered ground state of CoTiO$_3$ features ferromagnetic layers of Co$^{2+}$, stacked antiferromagnetically along the $c$-axis. We discover that the magnon dispersion relation exhibits strong easy-plane exchange anisotropy and hosts a clear gapless Dirac cone along the edge of the 3D Brillouin zone. Our results establish CoTiO$_3$ as a model pseudospin-$1/2$ material to study interacting Dirac bosons in a 3D quantum XY magnet.

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Bo Yuan, Ilia Khait, Guo-Jiun Shu, F. C. Chou, M. B. Stone, J. P. Clancy, Arun Paramekanti, Young-June Kim. 2019-07-03. Dirac magnons in a honeycomb lattice quantum XY magnet CoTiO3. https://doi.org/10.1103/physrevx.10.011062

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