Impact of spin-orbit splitting on two-photon absorption spectra in a halide perovskite single crystal

Metal halide perovskites have emerged as versatile photonic device materials because of their outstanding optical properties. Here, we report the two-photon absorption (TPA) spectra for $\mathrm{C}{\mathrm{H}}_{3}\mathrm{N}{\mathrm{H}}_{3}\mathrm{Pb}{\mathrm{Br}}_{3}$ perovskite single crystals under linearly and circularly polarized laser pulses. We experimentally determined the spin-orbit splitting energy from the TPA linear-circular dichroism spectrum and found the higher-energy band around 0.8 eV above the band edge. From a theoretical analysis of the experimental data, we evaluated the exciton binding energy and the exciton reduced mass. Our findings provide essential information on the electronic structures and carrier dynamics of halide perovskites.