Spin Filtering Properties of Structures Based on Stanene and Bismuthene Nanoribbons with Magnetism

This is the authors' abstract. We don't add key points for this paper.

The transport properties of spin filters based on two-dimensional magnetic topological insulators (TI) are theoretically studied, exploiting the spin-polarized quantum-anomalous-Hall effect in these materials. The electron transport properties of these structures are explored through the non-equilibrium-Green’s-functon(NEGF) formalism. We first considered the spin-filtering properties of heterostructures based on non-magnetic TI/antiferromagnetic TI heterostructures, using a Kane-Mele tight-binding Hamiltonian model. Our results reveal that a gate bias of about 2 V is required to obtain an order of magnitude drop in the minority spin current of these heterostructures. In a search for magnetic TIs suitable for these applications, we investigate the electronic and magnetic properties of stanene and bismuthene nanoribbons with metal edge modification, using density functional theory (DFT) simulations. The direction of the magnetic moment is found to be heavily influenced by the electric field, while the magnitude of the magnetic moment declines drastically. Additionally, the role of edge oxidization on the magnetic state of stanene nanoribbons is explored, and a noticeable impact is observed. We next study the spin filtering properties of stanene and bismuthene ribbons with magnetism only at one edge, using NEGF based on DFT Hamiltonians. The transport characteristics exhibit noticeable spin polarization, without requiring an applied electric field along the out-of-plane direction. We also show that one edge magnetization can be induced in stanene nanoribbons with asymmetric edge passivation; DFT simulations predict the formation of one-way helical edge states in these structures. The results presented herein provide insight into the transport properties of magnetic TIs and their possible applications in spin filters and qubits based on Majorana bound states.