Exciton quantum phases of Bose-Einstein condensation, exciton insulators, and superfluidity are largely governed by exciton-exciton interactions. Manipulating these interactions has sparked tremendous efforts to investigate quantum-confined excitons in two-dimensional (2D) semiconductors. In typical 2D exciton systems, however, strong dipolar interactions can be accessible at the cost of optical deactivation with significantly reduced oscillator strengths. Here we observe an emergent dipolar exciton with strong interactions in 2D perovskites with a surface lattice reconstruction. To unravel the microscopic nature of this exciton, we synergistically combine extensive optical spectroscopy, quantum-confined Stark effect, and density functional theory calculations. The dipolar exciton features dominant in-plane (IP) transition dipole moments, alongside coexisting out-of-plane (OP) electric dipole moments, giving rise to an exciton-exciton interaction strength of 38.1 ± 6.7 μeV·μm2 as one of the highest reported to date. The observation promises great potential to explore quantum phenomena and optoelectronic applications based on strongly interacting dipolar excitons in 2D semiconductors.
Hu et al. (Mon,) studied this question.