Two-dimensional dilute magnetic semiconductors can provide fundamental insights in the very nature of magnetic orders and their manipulation through electron and hole doping. Despite the fundamental physics, due to the large charge density control ca
pability in these materials, they can be extremely important in spintronics applications such as spin valve and spin-based transistors. In this article, we studied a two-dimensional dilute magnetic semiconductors consisting of phosphorene monolayer doped with cobalt atoms in substitutional and interstitial defects. We show that these defects can be stabilized and are electrically active. Furthermore, by including holes or electrons by a potential gate, the exchange interaction and magnetic order can be engineered, and may even induce a ferromagnetic-to-antiferromagnetic phase transition in p-doped phosphorene.
The optical response of phosphorene can be gradually changed by application of moderate uniaxial compression, as the material undergoes the transition into an indirect gap semiconductor and eventually into a semimetal. Strain tunes not only the gap b
etween the valence band and conduction band local extrema, but also the effective masses, and in consequence, the exciton anisotropy and binding strength. In this article, we consider from a theoretical point of view how the exciton stability and the resulting luminescence energy evolves under uniaxial strain. We find that the exciton binding energy can be as large as 0.87 eV in vacuum for 5% transverse strain, placing it amongst the highest for 2D materials. Further, the large shift of the luminescence peak and its linear dependence on strain suggest that it can be used to probe directly the strain state of single-layers.
