Strain-induced spin-gapless semiconductors and pure thermal spin-current in magnetic black arsenic-phosphorus monolayers

Spin-gapless semiconductor (SGS) materials are regarded as the most promising candidates for ideal massless and dissipationless states towards low-power spintronic device applications. Here, we propose a spin-gapless semiconducting black arsenic-phosphorus (AsP) monolayer halogenated by chlorine (Cl) adatoms and reveal the perfect spin Seebeck effect induced by its SGS character to produce pure thermal spin-current using first-principles calculations. Our results show that Cl atoms prefer to adsorb P atoms rather than As atoms in the AsP monolayer, behaving as a ferromagnetic semiconductor. The As-adsorbed AsP monolayer as an ideal SGS material with parabolic-type energy dispersion can be utilized to realize symmetrical spin Seebeck current for perfect pure thermal spin-current even at an extremely low on-off temperature. Moreover, in-plane strain engineering can effectively manipulate the electronic structures of the P-absorbed AsP monolayer for perfect parabolic-type SGS similar to As-adsorbed AsP, and to obtain the relevant thermoelectric effect. These distinct features suggest the potential applications of the Cl-halogenated AsP monolayer with the SGS character in low-power spin-caloritronic devices.