Signatures of three-state Potts nematicity in spin excitations of the van der Waals antiferromagnet FePSe$_3$

Weiliang Yao; Viviane Peçanha Antonio; Devashibhai Adroja; S. J. Gomez Alvarado; Bin Gao; Sijie Xu; Ruixian Liu; Xingye Lu; Pengcheng Dai

doi:10.1021/acs.nanolett.5c06293

arXiv · 2509.02475

Signatures of three-state Potts nematicity in spin excitations of the van der Waals antiferromagnet FePSe$_3$

Weiliang Yao·Viviane Peçanha Antonio·Devashibhai Adroja·S. J. Gomez Alvarado·Bin Gao·Sijie Xu·Ruixian Liu·Xingye Lu·Pengcheng Dai

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Abstract

In two-dimensional (2D) nearly square-lattice quantum materials, electron correlations can induce an electronic nematic phase with twofold rotational ($C_2$) symmetry that profoundly impacts their properties. For 2D materials with threefold rotational ($C_3$) symmetry, such as the honeycomb lattice, a vestigial three-state Potts nematic order has been observed in the van der Waals antiferromagnet (AFM) FePSe$_3$ via optical and thermodynamic methods under uniaxial strain. Here, we use neutron scattering to study the magnetic order and spin excitations of FePSe$_3$ under uniaxial strain. In the AFM ordered state, we find that $\sim$0.6% tensile strain significantly suppresses one zigzag domain and promotes the other two, lowering the AFM order and spin waves to $C_2$ symmetry. The broken $C_3$ symmetry in spin excitations persists slightly above $T_{\rm{N}}\approx 108.6$ K, where the zigzag AFM order is absent. Our results thus provide direct evidence of magnetoelastic coupling and suggest that the three-state Potts nematicity in paramagnetic spin excitations arises from the vestigial order associated with the low-temperature zigzag AFM order.

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Weiliang Yao, Viviane Peçanha Antonio, Devashibhai Adroja, S. J. Gomez Alvarado, Bin Gao, Sijie Xu, Ruixian Liu, Xingye Lu, Pengcheng Dai. 2025-09-02. Signatures of three-state Potts nematicity in spin excitations of the van der Waals antiferromagnet FePSe$_3$. https://doi.org/10.1021/acs.nanolett.5c06293

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