This paper demonstrates that the recently synthesized MoSi₂N₄ is an ideal 2D semiconductor with robust band edge states protected from capricious environmental chemical coupling effects. Many-body perturbation theory calculations show how MoSi₂N₄'s band edge states are shielded from direct chemical coupling, while its quasiparticle and excitonic properties are tunable through nonlocal dielectric screening. This, along with its moderate band gap and stability, suggests potential applications in energy, 2D electronics, and optoelectronics.
