▎ 摘　　要

Within the frame of Huang-Rhys's lattice relaxation model, we theoretically investigate the carrier relaxation mediated by two-phonon processes, which consists in polar surface optical phonon and longitudinal acoustic phonon emission between the Landau levels of graphene on different polar substrates. This two-phonon relaxation process is very fast within the picosecond scale and may seriously hinder the carrier multiplication based on effective Auger processes. Moreover, the polarizability of the polar substrate plays an important role in determining the relaxation time. These results could be helpful in designing graphene-based photoelectric and photodetector devices. Copyright (C) EPLA, 2014