Year: 2026
Type: preprint
Abstract: 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$_3$.
Source: arXiv (Cornell University)
Authors: Matsuura, Shuta, Imai, Shohei, Tsuji, Naoto
Institution: The University of Tokyo
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Awards: G1818204041, Real and reciprocal spacetime imaging of many-body excitons and quantum phase control, Development of Quantum Material Control Methods Utilizing the Quantum Nature of Light, Foundation of Nonclassical Nonlinear Photophysics: Exploring Quantum Correlations between Quantum Light and Solids, G8868583067
OpenAlex ID: W7212505949