Electronic, magnetic and optical properties of MnPX (X = S, Se) monolayers with and without chalcogen defects: a first-principles study.

Based on density functional theory (DFT), we performed first-principles studies on the electronic structure, magnetic state and optical properties of two-dimensional (2D) transition-metal phosphorous trichalcogenides MnPX (X = S and Se). The calculated interlayer cleavage energies of the MnPX monolayers indicate the energetic possibility to be exfoliated from the bulk phase, with good dynamical stability confirmed by the absence of imaginary contributions in the phonon spectra. The MnPX monolayers are both Néel antiferromagnetic (AFM) semiconductors with direct band gaps falling into the visible optical spectrum.