  We study theoretically the exciton Bose-Einstein condensation and exciton
vortices in a two-dimensional (2D) perovskite (PEA)2PbI4 monolayer. Combining
the first-principles calculations and the Keldysh model, the exciton binding
energy of (PEA)2PbI4 in a monolayer can approach hundreds 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 presence of perpendicular electric fields, the
dipole-dipole interaction between excitons is found to drive the condensed
excitons into patterned vortices, as the evolution time of vortex patterns is
comparable to the exciton lifetime.
