音 賢一

Monolayer materials are strongly affected by their potential fluctuations, which are induced by an intrinsic corrugation or the surface roughness of the substrate. We compare the effective exciton-exciton annihilation (EEA) rate constants of monolayer WS2 on substrates with different surface topographies. We show that monolayer WS2 on the substrate with atomically flat terraces displays small effective EEA rate constant deviating from the overall tendency and multiple exciton decay components, which cannot be accounted for by a conventional EEA model. To obtain a correct description, we use a quantized EEA model. The intrinsic EEA rate constant for the flat-terrace substrates determined by this new model is comparable to that of hBN-encapsulated monolayer WS2.

We investigate the electron-phonon coupling in CH3NH3PbX3 lead halide perovskites through the observation of Landau levels and high-order excitons at weak magnetic fields, where the cyclotron energy is significantly smaller than the longitudinal optical phonon energy. The reduced masses of the carriers and the exciton binding energies obtained from these data are clearly influenced by polaron formation. We analyze the field-dependent polaronic and excitonic properties, and show that they can be quantitatively reproduced by the Frohlich large polaron model.

Carrier mobility is one of the most fundamental material parameters of semiconductors and requisite for device applications and interpretation of physical phenomena. We determined the electron and hole mobilities of a CH3NH3PbBr3 single crystal in the high-carrier density regime by combining AC Hall measurements under photoexcitation and two-carrier analysis. Both electron and hole mobilities were significantly enhanced by photo-doping and exceeded 300 cm(2) V-1 s(-1), which are comparable to the electron Hall mobilities of conventional inorganic semiconductors. Our experimental results indicate that charged dislocation scattering dominates the carrier transport at room temperature in the low-carrier density regime.