Large exciton binding energies in MnPS3 as a case study of a van der Waals layered magnet

Stable excitons in semiconductor monolayers such as transition-metal dichalcogenides (TMDCs) enable and motivate fundamental research as well as the development of room-temperature optoelectronics applications. The newly discovered layered magnetic materials present a unique opportunity to integrate optical functionalities with magnetism. We predict that a large class of antiferromagnetic semiconducting monolayers of the MP X3 family exhibit giant excitonic binding energies, making them suitable platforms for magneto-optical investigations and optospintronics applications. Indeed, our investigations, based on first-principles methods combined with an effective-model Bethe-Salpeter solver, show that excitons in bare Neel- MnPS3 are bound by more than 1 eV, which is twice the excitonic energies in TMDCs. In addition, the antiferromagnetic ordering of monolayer samples can be inferred indirectly using different polarization of light.