Electronic transport and spin-valley polarization in ferromagnetic 8-Pmmn borophene junctions

Abstract 8-Pmmn borophene is a very attractive 2D material from both the fundamental and technological standpoints. Its tilted band structure gives rise to exotic phenomena such as the oblique Klein tunneling and its gated junction directional dependence represents an additional degree of freedom that can be used to modulate the spin-valley electronic transport. Spin and valley polarization are possible in ferromagnetic 8-Pmmn borophene junctions by having precise control of the transverse wave vector as well as by appropriately tuning the electrostatic and magnetic gating. Here, we show that when only the magnetization is applied, valley polarization is not possible when all transverse wave vectors are considered due to the equivalence between the valley conductance components. On the contrary, the difference between the spin conductance components gives rise to Fermi energy regions of almost perfect spin polarization. These regions can be increased by placing the ferromagnetic gates in an oblique direction. Also, perfect positive and negative spin polarization states are accessible by reversing the magnetization direction. The valley degeneracy is lifted by considering an external magnetic field, generating regions of perfect positive and negative valley polarization. When the external magnetic field and magnetization are considered simultaneously, the spin-valley conductance degeneracy is broken allowing simultaneous regions of perfect spin and perfect valley polarization. These findings indicate that ferromagnetic 8-Pmmn borophene junctions could be the basis for spintronic and valleytronic device applications.