Strain modulation on the spin transport properties of PTB junctions with MoC2 electrodes

Based on MoC₂ nanoribbons and poly-(terphenylene-butadiynylene) (PTB) molecules, we designed MoC₂-PTB molecular spintronic devices and investigated their spin-dependent electron transport properties by using spin-polarized density functional theory and the non-equilibrium Green's function method. As a typical MXene material, it is found that the magnetic contribution of MoC₂ nanoribbons mainly comes from the delocalized 3d electron of edge Mo atoms. Owing to the obvious spin-splitting near the Fermi level of the MoC₂ nanoribbon electrode, the spin states can be effectively injected into the central scattering region under an external bias voltage. In addition, we also studied the effects of z-axis strain on the spin transport properties of the PTB molecular device, where the strain was controlled within the range of -9% to 9%. Under a compressed strain, spin current increases obviously, and the spin-filtering efficiency (SFE) decreases slightly. Nevertheless, under a tensile strain, we found that the SFE increases but spin current decreases. Moreover, z-axis strain can induce a negative differential resistance (NDR) effect at a high bias point. This work would expand the potential applications of new two-dimensional (2D) materials in the field of molecular spintronic devices.

Electrical controllable spin pump based on a zigzag silicene nanoribbon junction

We propose a possible electrical controllable spin pump based on a zigzag silicene nanoribbon ferromagnetic junction by applying two time-dependent perpendicular electric fields. By using the Keldysh Green's function method, we derive the analytic expression of the spin-resolved current at the adiabatic approximation and demonstrate that two asymmetric spin up and spin down currents can be pumped out in the device without an external bias. The pumped currents mainly come from the interplay between the photon-assisted spin pump effect and the electrically-modulated energy band structure of the tunneling junction. The spin valve phenomena are not only related to the energy gap opened by two perpendicular staggered potentials, but also dependent on the system parameters such as the pumping frequency, the pumping phase difference, the spin-orbit coupling and the Fermi level, which can be tuned by the electrical methods. The proposed device can also be used to produce a pure spin current and a 100% polarized spin current through the photon-assisted pumping process. Our investigations may provide an electrical manipulation of spin-polarized electrons in graphene-like pumping devices.

High performance bipolar spin filtering and switching functions of poly-(terphenylene-butadiynylene) between zigzag graphene nanoribbon electrodes

Using the nonequilibrium Green’s function method combined with spin-polarized DFT, we investigate the spin-resolved electronic transport properties of devices made of poly-(terphenylene-butadiynylene) (PTB) between zigzag graphene nanoribbon (ZGNR) electrodes.