Full spin polarization and pure spin current produced by the photogalvanic effect in penta-PdN2 photodetector

The photogalvanic effects (PGEs) in low-dimensional devices were thought to be an important mechanism to generate pure spin current which was a essential problem in spintronics. Herein, based on non-equilibrium Green's function combined with density functional theory, we studied linear and elliptical spin dependent PGEs in the photodetector based on the penta-PdN2 monolayer at zero bias. Due to spin-orbit coupling originating from the heavy metal atoms Pd and low symmetry of C2v for the pristine case and Cs for the defect cases, the penta-PdN2 photodetector at pristine, vacancy and substitution-doping situations can produce robust spin dependent PGEs, and the import of defects were able to strengthen the linear and elliptical PGEs, respectively. More importantly, on account of enormous splitting of the DOS for the pristine, Pd-vacancy, N2-vacancy and NNvacancy cases, spin up and spin down photocurrents accordingly formed spin splitting, which eventually led to full spin polarization and then pure spin currents in the penta-PdN2 photodetector. PdSe2 monolayer has been compounded in experiments, so structurally similar penta-PdN2 monolayer possesses highly possible to be prepared. Therefore, if the penta-PdN2 photodetector can be successful assembled, the spin-generator will be reality, even no need to be doped because the pristine penta-PdN2 photodetector can give rise to pure spin currents. In addtion, the penta-PdN2 photodetector at different situations are highly polarization sensitive. In conclude, our work suggested great potential applications of the penta-PdN2 monolayer on PGE-driven low energy-consumption photodetectors and spin-generators in optoelectronics and spintronics.