Terahertz Magnonics in 2D Chromium Trihalides with Atomically-Engineered Dzyaloshinskii–Moriya Interaction

Abstract

Two-dimensional (2D) magnetic materials, such as chromium trihalides and manganese dichalcogenides, have recently drawn immense attention of both theoretical and experimental research, due to both fundamental significance and promising technological applications. Particularly, some chromium trihalides have been shown able to host terahertz spin-waves (SW) [1] and are promising candidates for ultra-fast information transport and processing based on magnons. In this work we investigated the spin-wave propagation in the presence of strategically-placed defects (halide vacancies) in the honeycomb structure of chromium trihalides. We performed Density Functional Theory (DFT) calculations to obtain the magnetic parameters of the considered structures, followed by spin-dynamics simulations of the SW propagation. We reveal that the lattice defects host strong Dzyaloshinskii–Moriya interaction (DMI), so that a designed pattern of defects can serve as a spin-wave guide. We show the spectra of spin-waves propagating across periodic defect lines that prove such structures can work as a magnonic crystal [2] for terahertz SWs, exhibiting key features such as band gaps where SWs are not allowed to propagate. Such broad degree of manipulations available in 2D materials therefore suggests these systems as a front-runner for terahertz magnonics, applicable in cutting-edge devices.