Polaron Mass and Exciton Energy of CH3NH3PbX3 Revealed by Landau Level Spectroscopy Under Low Magnetic Fields

We investigate the electron-phonon coupling of CH3NH3PbX3 lead halide perovskites through the observation of Landau levels and high-order excitons under weak magnetic fields, where the cyclotron energy is sufficiently smaller than the LO phonon energy. Our low-field data provide the carrier reduced masses and exciton binding energies of halide perovskites in the presence of a strong polaron effect. We analyze the field-dependent excitonic properties and discuss the large mass enhancement beyond the conventional Frohlich polaron model.