Pure spin and valley injections into silicene by nonlocal transports

The spin and valley current injections into graphene-like materials still face tough challenges. Here we theoretically propose a nonlocal method for pure spin and valley currents injected into a silicene-based ferromagnetic/superconducting/normal junction, with two electric fields perpendicularly applied to the ferromagnetic and normal regions, respectively. We demonstrate that by the joint control of an exchange field and the electric fields, there are two competing nonlocal transport processes in this system: the elastic cotunneling and the crossed Andreev reflection, which are utilized to generate the different spin and valley polarized currents in opposite directions. It is shown that under the proper conditions, even pure spin and valley currents can be obtained and injected into the normal region without accompanying of charge currents. Moreover, the injected spin and valley currents could be controlled synchronously or separately by modulating the applied electric fields. In addition, we also discuss that for different superconductor length, the polarized directions of the injected spin and valley currents could change. These results are expected to be helpful for designing an efficient silicene-based spin and valley current injector.