Spin-charge Dynamics in Topological Insulator Low-dimensional Ferromagnet Heterostructures

The recent experimental realization of two-dimensional (2D) ferromagnetic (FM) crystals like CrI₃ and CrGeTe₃ has sparked great interest with possible use in applications ranging from, spintronics, valleytronics, and application in magnetic memories. The low out-of-plane anisotropy and the experimental observation of 2D magnons in Cr-compounds, makes them an interesting candidate for fast memory devices. An interesting avenue of research lies in coupling 2D FMs with topological insulators (Tis). The edge states of topological insulators can act as spin-channels with high spin-polarizability. Moreover, depending on the direction of applied bias, the spin of the edge states can be switched due to spin-momentum locking. In this work, we theoretically model a 2D TI-FM heterostructure using an a tight-binding Hamiltonian for the TI and a Heisenberg Hamiltonian for the FM. We model the spin-charge dynamics using the non-equilibrium Green’s function and the time-quantified Monte-Carlo simulations. We show that by applying an electric bias on the 2D TI, the magnetic domain of the 2D FM can be switched. We finally show that the magnetic order of 2D FM also impacts the transport in the interfacing 2D TI, which can be used to design ultrafast memory devices.