Exciton-phonon coupling induces new pathway for ultrafast intralayer-to-interlayer exciton transition and interlayer charge transfer in WS2-MoS2 heterostructure: a first-principles study
arxiv(2024)
摘要
Despite the weak, van-der-Waals interlayer coupling, photoinduced charge
transfer vertically across atomically thin interfaces can occur within
surprisingly fast, sub-50fs timescales. Early theoretical understanding of the
charge transfer is based on a noninteracting picture, neglecting excitonic
effects that dominate the optical properties of such materials. Here, we employ
an ab initio many-body perturbation theory approach which explicitly accounts
for the excitons and phonons in the heterostructure. Our large-scale
first-principles calculations directly probe the role of exciton-phonon
coupling in the charge dynamics of the WS_2/MoS_2 heterobilayer. We find
that the exciton-phonon interaction induced relaxation time of photo-excited
excitons at the K valley of MoS_2 and WS_2 is 67 fs and 15 fs at 300 K,
respectively, which sets a lower bound to the intralayer-to-interlayer exciton
transfer time and is consistent with experiment reports. We further show that
electron-hole correlations facilitate novel transfer pathways which are
otherwise inaccessible to non-interacting electrons and holes.
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