Novel characterization of spin waves in twisted CrSBr/CrSBr heterostructures via DFT/QFT modeling and experiments

We present a combined experimental, density functional theory (DFT), and quantum field theory (QFT) approach to understanding spin waves in twisted 2D magnetic heterojunctions. In particular, we investigate twisted CrSBr/CrSBr bilayers to reveal how interlayer twist angles and structural variations affect spin-wave generation, propagation, and coherence. Experimentally, we fabricate twisted CrSBr heterostructures with controlled rotation angles and probe their steady-state and time-resolved optical responses as functions of twist angle, magnetic field, and temperature. Using the spatially resolved pump–probe spectroscopy, we directly image spin-wave propagation in twisted regions and compare the amplitude and frequency distributions to those in pristine CrSBr. Complementary DFT calculations provide the local atomic geometry and exchange coupling parameters, which are incorporated into a QFT framework to model spin-wave dispersion relations in twisted and defect-engineered structures. By correlating theoretical dispersion features with experimentally mapped spin-wave dynamics, this integrated methodology reveals how interlayer twist and nanoscale morphology affect magnon behavior in van der Waals magnets.