Observation of topological $Z_2$ vortex fluctuations in the frustrated Heisenberg magnet NaCrO${}_2$

Abstract

Spin fluctuations in the triangular-lattice Heisenberg antiferromagnet NaCrO${}_2$ are investigated by means of quasi-elastic neutron scattering with high energy resolution and wide energy band. Two components with the following features are captured separately. They are pronounced at intermediate temperatures of 20-50 K. One with quite an extended lifetime corresponding to $\sim$$0.001E_{\mathrm{ex}}$ ($E_{\mathrm{ex}}$ the exchange energy) nearly disappears at low temperature 10 K, and the other with an extended lifetime $\sim$$0.01E_{\mathrm{ex}}$ survives there, identified as free $Z_2$ vortex and $Z_2$-vortex pair, respectively, in harmony with the $Z_2$ vortex theory.

Contents and discussion are expanded, including new figures in Appendix. To appear in Phys. Rev. B

References in corpus (8)

• Unconventional Dynamics in Triangular Heisenberg Antiferromagnet NaCrO2
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Cited by in corpus (3)

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• ${\mathbb{Z}}_2$ Vortex Crystals in Tetrahedral Antiferromagnets: Fractional Charges and Topological Magnons