Optical Absorption in Monolayer SnO2

Large exciton binding energy due to nonlocal screening effect that is even weaker in monolayer SnO2 because of the narrow spatial overlap of the density of occupied and unoccupied states. Because of this narrow spatial extension of the wave function of states in the proximity of the Fermi level coupled with the long-ranged electron- hole interactions, the exciton radius will be reduced leading to higher binding energy!