Microscopic Evidence for a Zhang-Rice Triplet State in the van der Waals Antiferromagnet, NiPS3 (published in PRL)
NiPS3 is one of representative van der Waals antiferromagnets which exhibit unusual light-matter interaction coupled with the magnetic order. It exhibits a highly coherent many-body exciton peak (< 0.5 meV linewidth) around 1.478 eV under a low-temperature zigzag magnetic order, which vanishes when the magnetic order breaks down. While early studies proposed a Zhang-Rice model driven by entanglement between S 3p and Ni 3d holes, various alternative scenarios have left the exact physical mechanism unresolved. The origin of this excitation has been heavily debated until now.
To address this, Prof. Park’s team, in collaboration with Changwon National University, synthesized 33S-substituted NiPS3 and conducted Nuclear Magnetic Resonance (NMR) measurements. By comparing and analyzing 33S and 31P NMR results, we identified definitive microscopic evidence that self-doped ligand holes strongly entangle with Ni holes, realizing the Zhang-Rice triplet state. Furthermore, temperature-dependent 33S spin-lattice relaxation time analysis revealed the presence of spin nematic fluctuations driven by spin-charge interactions.
By directly validating the many-body quantum states of a van der Waals magnet via microscopic techniques, this study provides a crucial foundation for understanding the fundamental properties and unique light-matter interactions of 2D magnetic materials.
Autors : Beom Hyun Kim, Youjin Lee, Junik Hwang, Junghyun Kim, Je-Geun Park, and Seung-Ho Baek