Spin caloritronics of blue phosphorene nanoribbons

We report a first-principles study of the magnetic properties and spin caloritronics of zigzag-type blue phosphorene nanoribbons (zBPNRs). It is found that the bare zBPNR (0H-zBPNR) or monohydrogenated zBPNR (1H-zBPNR) exhibit spin-semiconducting properties arising from the edge electronic states. We further confirm that the p(y) orbitals of the edge P atoms have the main contributions to these states. The spin-semiconducting property has a natural advantage for fabricating perfect thermospin devices with a stronger spin Seebeck effect than charge Seebeck effect at the Fermi level. When a temperature difference is applied, the electric current with the different spin index displays a bipolar behavior, and the spin-filtering efficiency can reach 1200%. By changing the widths of 0H-zBPNR and 1H-zBPNR, the ratio of the spin Seebeck coefficient to the charge Seebeck coefficient at the Fermi level is about 10 at room temperature.