Third-Order Optical Nonlinearity Due to Excitons and Biexcitons in a Self-Organized Quantum-Well Material (C₆H₁₃NH₃)₂PbI₄

Third-order optical nonlinearity around the exciton resonance in (C 6 H 13 NH 3 ) 2 PbI 4 was measured using time-integrated and spectrally-resolved four-wave-mixing (FWM) techniques. For excitation below the exciton resonance, biexciton contribution to the FWM signals was observed. The dephasing energy of the biexcitons was estimated to be larger than 10 meV.