The half-metallicity and the spin filtering, NDR and spin Seebeck effects in 2D Ag-doped SnSe monolayer.

Two-dimensional SnSe has become more and more attractive due to the excellent electronic, optoelectronic, and thermoelectric properties. However, the study on magnetic properties is rare. Inspired by the recent experimental synthesis of SnSe monolayer and Ag-doped SnSe thin films, we use the first-principles calculations combined with the nonequilibrium Green's function method to investigate the structural, electronic, magnetic, and spin transport properties of an Ag-doped SnSe monolayer. It is found that the doped system exhibits half-metallic ferromagnetism with the energy gap of about 0.5 eV in the spin-down channel. The spin-polarized transport properties based on Ag-doped SnSe monolayers show an excellent spin filtering effect and a negative differential resistance effect under a bias voltage. Interestingly, under a temperature gradient, the spin Seebeck effect and the temperature-controlled reverse of spin polarization are also observed. These perfect spin transport properties can be understood from the calculated spin-polarized band structure and the spin-polarized transport spectrum. These studies indicate the potential spintronic and spin caloritronic applications for Ag-doped SnSe monolayer.