Investigation on Spin Band-Pass Filters Utilizing Two-Dimensional Topological Insulators with an Embedded Rectangular Cavity

Precise control of spin currents in topological insulators (TIs) remains a significant challenge for the development of spintronics. By enhancement of the intrinsic spin–orbit coupling (ISOC) of graphene nanoribbons (GNRs), they can exhibit the characteristics of TIs and serve as promising candidates for high-performance spintronic devices. Spin transport in the devices of TIs with Rashba spin–orbit coupling (RSOC) under a magnetic field is thoroughly investigated in this work using recursive Green’s function approaches, incorporating Landau theory and corrections for the Peierls phase. These findings reveal a linear dependence of spin conductance on magnetic flux resulting from the interaction of SOC effects and Landau level quantization induced by the magnetic field. More computations utilizing the nonequilibrium Keldysh Green’s function formalism have demonstrated that Ising-symmetric and XY-symmetric magnetic defects enable the creation and control of spin-polarized currents at discrete energies and throughout continuous energy ranges, respectively. These results provide significant insights for developing a novel spin band-pass filter that integrates synergistic control of local magnetic field and magnetic defects.