Magnetically propagating Hund's exciton in van der Waals antiferromagnet NiPS3

W He; Y Shen; K Wohlfeld; J Sears; J Li; J Pelliciari; M Walicki; S Johnston; E Baldini; V Bisogni; M Mitrano; M P M Dean

doi:10.1038/s41467-024-47852-x

Magnetically propagating Hund's exciton in van der Waals antiferromagnet NiPS₃

Nat Commun. 2024 Apr 25;15(1):3496. doi: 10.1038/s41467-024-47852-x.

Authors

W He¹, Y Shen², K Wohlfeld³, J Sears², J Li⁴, J Pelliciari⁴, M Walicki³, S Johnston^{5

6}, E Baldini⁷, V Bisogni⁴, M Mitrano⁸, M P M Dean⁹

Affiliations

¹ Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY, 11973, USA. whe1@bnl.gov.
² Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY, 11973, USA.
³ Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Warsaw, PL-02093, Poland.
⁴ National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA.
⁵ Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, 37996, USA.
⁶ Institute of Advanced Materials and Manufacturing, The University of Tennessee, Knoxville, TN, 37996, USA.
⁷ Department of Physics, The University of Texas at Austin, Austin, TX, 78712, USA.
⁸ Department of Physics, Harvard University, Cambridge, MA, 02138, USA.
⁹ Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY, 11973, USA. mdean@bnl.gov.

Abstract

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.