Electron correlation effects on exchange interactions and spin excitations in 2D van der Waals materials

Despite serious effort, the nature of the magnetic interactions and the role of electron-correlation effects in magnetic two-dimensional (2D) van der Waals materials remains elusive. Using CrI3 as a model system, we show that the calculated electronic structure including nonlocal electron correlations yields spin excitations consistent with inelastic neutron-scattering measurements. Remarkably, this approach identifies an unreported correlation-enhanced interlayer super-superexchange, which rotates the magnon Dirac lines off, and introduces a gap along the high-symmetry Gamma -K-M path. This discovery provides a different perspective on the gap-opening mechanism observed in CrI3, which was previously associated with spin-orbit coupling through the Dzyaloshinskii-Moriya interaction or Kitaev interaction. Our observation elucidates the critical role of electron correlations on the spin ordering and spin dynamics in magnetic van der Waals materials and demonstrates the necessity of explicit treatment of electron correlations in the broad family of 2D magnetic materials.

Automated summary

This study investigates the nature of magnetic interactions and electron-correlation effects in 2D van der Waals materials using CrI3 as a model system. The calculated electronic structure, including nonlocal electron correlations, provides insights into spin excitations and reveals the critical role of electron correlations in spin ordering and dynamics in magnetic van der Waals materials. Additionally, a novel correlation-enhanced interlayer super-superexchange mechanism is identified, offering a different perspective on the gap-opening mechanism in CrI3.