Exciton Vortices in Two-Dimensional Hybrid Perovskite Monolayers

We study theoretically the exciton Bose–Einstein condensation and exciton vortices in a two-dimensional (2D) perovskite (PEA)_2PbI_4 monolayer. Combining the first-principles calculations and the Keldysh model, the exciton binding energy of in a (PEA)_2PbI_4 monolayer can approach hundreds of meV, which make it possible to observe the excitonic effect at room temperature. Due to the large exciton binding energy, and hence the high density of excitons, we find that the critical temperature of the exciton condensation could approach the liquid nitrogen regime. In the presence of perpendicular electric fields, the dipole-dipole interaction between excitons is found to drive the condensed excitons confined in (PEA)_2PbI_4 monolayer flakes into patterned vortices, as the evolution time of vortex patterns is comparable to the exciton lifetime.