Observation of Two-Photon Resonant Raman Scattering via the Biexciton Level in Two-Dimensional Halide Perovskite (C6H5C2H4NH3)2PbI4

초록

2D halide perovskites provide an excellent system for investigating fundamental properties of excitons due to strong quantum and dielectric confinements, yet biexciton-related phenomena remain largely unexplored. Here, we report two-photon resonant Raman scattering (TRRS) in (PEA)2PbI4 (PEA = C6H5C2H4NH3), enabled by the biexciton level acting as an intermediate state. TRRS shows a distinct threshold behavior, causing an emergent sharp Raman peak superimposed on the biexciton photoluminescence spectrum. The TRRS threshold is 88.5 MW/cm2 at 10 K, which gradually increases with temperature up to 379.7 MW/cm2 at 90 K. Unlike coexisting amplified spontaneous emission, this Raman peak shifts by 2 Delta omega 1 when the excitation frequency (omega 1) is tuned by Delta omega 1 near 2329.9 meV, which is the resonant two-photon energy for the direct generation of biexcitons. Consistent with two-photon selection rules, TRRS is inactive under co-circularly polarized excitation. Our findings highlight strong nonlinear optical properties of the perovskite and underscore its potential for biexciton-based applications.

키워드