Dimensionality dependent electronic structure of the exfoliated van der Waals antiferromagnet NiPS3

Abstract

Resonant Inelastic X-ray Scattering (RIXS) was used to measure the local electronic structure in few-layer exfoliated flakes of the van der Waals antiferromagnet NiPS3. The resulting spectra show a systematic softening and broadening of NiS6 multiplet excitations with decreasing layer count from the bulk to three atomic layers (3L). These trends are driven by a decrease in the transition metal-ligand and ligand-ligand hopping integrals, and in the charge-transfer energy: Δ = 0.60 eV in the bulk and 0.22 eV in 3L NiPS3. Relevant intralayer magnetic exchange integrals computed from the electronic parameters exhibit a systematic decrease in the average interaction strength with thickness and place 2D NiPS3 close to the phase boundary between stripy and spiral antiferromagnetic order, which may explain the apparent vanishing of long-range order in the 2D limit. This study explicitly demonstrates the influence of interlayer electronic interactions on intralayer ones in insulating magnets. As a consequence, the magnetic Hamiltonian in few-layer insulating magnets can be significantly different from that in the bulk.

Daniel Staros

Chemistry

Annette Lopez

Physics

Brenda Rubenstein

Associate Professor of Chemistry and Physics