Amplitude mode in the planar triangular antiferromagnet Na${}_{0.9}$MnO${}_2$

Abstract

Amplitude modes arising from symmetry breaking in materials are of broad interest in condensed matter physics. These modes reflect an oscillation in the amplitude of a complex order parameter, yet are typically unstable and decay into oscillations of the order parameter's phase. This renders stable amplitude modes rare, and exotic effects in quantum antiferromagnets have historically provided a realm for their detection. Here we report an alternate route to realizing amplitude modes in magnetic materials by demonstrating that an antiferromagnet on a two-dimensional anisotropic triangular lattice ($\alpha$-Na${}_{0.9}$MnO${}_2$) exhibits a long-lived, coherent oscillation of its staggered magnetization field. Our results show that geometric frustration of Heisenberg spins with uniaxial single-ion anisotropy can renormalize the interactions of a dense two-dimensional network of moments into largely decoupled, one-dimensional chains that manifest a longitudinally polarized bound state. This bound state is driven by the Ising-like anisotropy inherent to the Mn${}^{3+}$ ions of this compound.

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Cited by in corpus (10)

• High order magnon bound states in the quasi-one-dimensional antiferromagnet $\alpha$-NaMnO${}_2$
• Dark Field X-ray Microscopy Below Liquid-Helium Temperature: The Case of NaMnO2
• Multimagnon dynamics and thermalization in the $S=1$ easy-axis ferromagnetic chain
• Nanoscale degeneracy lifting in a geometrically frustrated antiferromagnet
• Thermal evolution of quasi-1D spin correlations within the anisotropic triangular lattice of $\alpha$-NaMnO${}_2$
• Decoupling lattice and magnetic instabilities in frustrated CuMnO${}_2$
• Metastable and localized Ising magnetism in $\alpha$-CoV${}_2$O${}_6$ magnetization plateaus
• Cluster glass behavior of frustrated birnessites AxMnO2*yH2O (A = Na, K)
• Spin-chain correlations in the frustrated triangular lattice material CuMnO${}_2$
• Impurity-induced moment freezing in NaFe${}_x$Ru${}_{1-x}$O${}_2$