Spin nematic liquid crystal and scalar spin chirality in tetragonal lattice YbMnBi₂

@misc{xie2026spin,
  title = {{Spin nematic liquid crystal and scalar spin chirality in tetragonal lattice YbMnBi$_2$}},
  author = {Yaofeng Xie and Sijie Xu and Yu Pan and Taekoo Oh and Tingjun Zhang and Masaaki Matsuda and Zhaoyu Liu and Zehao Wang and Yiheng Wang and Siyu Pan and Avishek Maity and Sylwia Pawledzio and Xiaoping Wang and Songxue Chi and Feng Ye and Yiqing Hao and Huibo Cao and Barry L. Winn and Melissa K. Graves-Brook and Shuai Wu and Fan Li and Xiaoyuan Zhou and Claudia Felser and Naoto Nagaosa and Pengcheng Dai},
  howpublished = {arXiv},
  year = {2026},
  month = aug,
  doi = {10.48550/arxiv.2608.11776},
  eprint = {2608.11776},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.11776},
}

TY  - UNPB
TI  - Spin nematic liquid crystal and scalar spin chirality in tetragonal lattice YbMnBi_2
AU  - Yaofeng Xie
AU  - Sijie Xu
AU  - Yu Pan
AU  - Taekoo Oh
AU  - Tingjun Zhang
AU  - Masaaki Matsuda
AU  - Zhaoyu Liu
AU  - Zehao Wang
AU  - Yiheng Wang
AU  - Siyu Pan
AU  - Avishek Maity
AU  - Sylwia Pawledzio
AU  - Xiaoping Wang
AU  - Songxue Chi
AU  - Feng Ye
AU  - Yiqing Hao
AU  - Huibo Cao
AU  - Barry L. Winn
AU  - Melissa K. Graves-Brook
AU  - Shuai Wu
AU  - Fan Li
AU  - Xiaoyuan Zhou
AU  - Claudia Felser
AU  - Naoto Nagaosa
AU  - Pengcheng Dai
PY  - 2026
DA  - 2026/08/12
PB  - arXiv
DO  - 10.48550/arxiv.2608.11776
UR  - https://arxiv.org/abs/2608.11776
AB  - A spin nematic order, analogous to the nematic liquid crystal, characterizes the spontaneous breaking of spin-space rotational symmetry while preserving time-reversal (T) symmetry. In contrast, scalar spin chirality (SSC), a composite three-spin order, breaks T symmetry and is known to induce an anomalous Hall effect (AHE). Although a spin nematic phase has been suggested in frustrated magnets and the square-lattice iridate, how it might affect magnetotransport properties is unknown. Here we use polarized neutron scattering to show that tetragonal AMnBi_2 (A = Ca, Yb) is a strictly c-axis-aligned collinear antiferromagnet (C-type), with T_N ≈ 270 K and 290 K, respectively. On cooling from 450 K to T_N, low-energy spin excitations in YbMnBi_2 spontaneously change from isotropic to anisotropic in spin space within the tetragonal plane, forming a dynamic spin nematic phase around 400 K due to heavy Yb-induced spin-orbit coupling, before gapping out below T_N. Similar measurements on CaMnBi_2 reveal isotropic paramagnetic scattering without a spin nematic phase above T_N. Under an in-plane magnetic field, the Yb^3+ moments may interact with the dynamic spin nematic phase to induce nonzero SSC, giving rise to AHE and an anomalous Nernst effect (ANE) in YbMnBi_2 that are absent in CaMnBi_2 above T_N. A symmetry-based Ginzburg-Landau analysis shows that coupling terms between the nematic order and SSC are allowed under an external magnetic field, which could explain the rapid increase of AHE with field in YbMnBi_2. Our results provide compelling evidence for dynamic SSC-induced AHE and ANE in the paramagnetic phase of a compensated collinear antiferromagnet, opening a new avenue for the physics of composite spin orders and room-temperature spintronics without magnetic order.
ER  -