Magnetic van der Waals (vdW) materials have opened new frontiers for realizing novel many-body phenomena. Recently NiPS₃ has received intense interest since it hosts an excitonic quasiparticle whose properties appear to be intimately linked to the magnetic state of the lattice. Despite extensive studies, the electronic character, mobility, and magnetic interactions of the exciton remain unresolved. Here we address these issues by measuring NiPS₃ with ultra-high energy resolution resonant inelastic x-ray scattering (RIXS). We find that Hund’s exchange interactions are primarily responsible for the energy of formation of the exciton. Measuring the dispersion of the Hund’s exciton reveals that it propagates in a way that is analogous to a double-magnon. We trace this unique behavior to fundamental similarities between the NiPS₃ exciton hopping and spin exchange processes, underlining the unique magnetic characteristics of this novel quasiparticle.

磁性范德华（vdW）材料为实现新颖的多体现象开辟了新的领域。最近，NiPS ₃受到了人们的强烈关注，因为它含有一种激子准粒子，其特性似乎与晶格的磁性状态密切相关。尽管进行了广泛的研究，但激子的电子特性、迁移率和磁相互作用仍未得到解决。在这里，我们通过使用超高能量分辨率共振非弹性 X 射线散射 (RIXS)测量 NiPS ₃来解决这些问题。我们发现洪德交换相互作用主要负责激子形成的能量。测量洪德激子的色散表明它的传播方式类似于双磁振子。我们将这种独特的行为追溯到 NiPS ₃激子跳跃和自旋交换过程之间的基本相似性，强调了这种新型准粒子的独特磁性特征。