NiPS$_3$ 中多体激子的磁激活光学可见性
Magnetically activated optical visibility of many-body excitons in NiPS$_3$
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中文总结 AI 辅助
本研究通过群论分析和精确对角化，揭示NiPS$_3$中反铁磁序及三角畸变激活了原本禁止的多体激子光学跃迁，解释了其光学可见性。
中文摘要 AI 辅助
NiPS$_3$ 是一种层状范德华磁体，为探索激子与磁序之间的相互作用提供了独特平台。在其反铁磁相中，强多体相互作用产生了一种多体激子，表现为光学吸收光谱和光致发光中约 $1.47 \\, \mathrm{eV}$ 处异常尖锐的共振。先前的理论研究将局域基态和多体激子分别指定为自旋三重态和自旋单重态，两者均具有偶宇称。然而，这一图像无法解释所观察到的多体激子的光学可见性，因为根据自旋和宇称选择定则，这些态之间的一光子跃迁是被禁止的。在此，我们利用群论分析以及单团簇和双团簇模型的精确对角化，证明之字形反铁磁序打破了相关对称性，激活了原本被禁止的跃迁。我们进一步发现，局域配体环境的三角畸变和团簇间交换相互作用放宽了跃迁的额外空间和自旋约束，从而在光学电导率中产生可与光谱背景区分的激子信号。这些结果为 NiPS$_3$ 中多体激子的光学可见性及其与反铁磁序的联系提供了微观解释。
英文摘要
NiPS$_3$ is a layered van der Waals magnet that provides a unique platform for exploring the interplay between excitons and magnetic order. In its antiferromagnetic phase, strong many-body interactions give rise to a many-body exciton, which manifests itself as an exceptionally sharp resonance near $1.47 \, \mathrm{eV}$ in optical absorption spectra and photoluminescence. Previous theoretical studies have assigned the local ground state and the many-body exciton to spin-triplet and spin-singlet states, respectively, both with even parity. This picture, however, cannot account for the observed optical visibility of the many-body exciton because one-photon transitions between these states are forbidden by spin and parity selection rules. Here, using group-theoretical analysis and exact diagonalization of single- and two-cluster models, we show that zigzag antiferromagnetic order breaks the relevant symmetries and activates the otherwise forbidden transition. We further find that trigonal distortion of the local ligand environment and the inter-cluster exchange interaction relax additional spatial and spin constraints on the transition, producing an exciton signal in the optical conductivity that is distinguishable from the spectral background. These results provide a microscopic explanation for the optical visibility of the many-body exciton and its connection to antiferromagnetic order in NiPS$_3$.
发表机构
- University of Tokyo（东京大学）
- RIKEN Center for Emergent Matter Science (CEMS)（理化学研究所 emergent matter science center）
- Trans-scale Quantum Science Institute, University of Tokyo（东京大学 跨尺度量子科学研究所）
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