Based on \emph{ab initio} theoretical calculations of the optical spectra of vertical heterostructures of MoSe2 (or MoS2) and WSe2 sheets, we reveal two spin-orbit-split Rydberg series of excitonic states below the \textsl{A} excitons of MoSe2 and WSe2 with a significant binding energy on the order of 250\,meV for the first excitons in the series. At the same time, we predict crystalographically aligned MoSe2/WSe2 heterostructures to exhibit an indirect fundamental band gap. Due to the type-II nature of the MoSe2/WSe2 heterostructure, the indirect transition and the exciton Rydberg series corresponding to a direct transition exhibit a distinct interlayer nature with spatial charge separation of the coupled electrons and holes. The experimentally observed long-lived states in photoluminescence spectra of MoX2/WY2 heterostructure are attributed to such interlayer exciton states. Our calculations further suggest an effect of stacking order on the peak energy of the interlayer excitons and their oscillation strengths.
@article{arxiv.1801.06310,
title = {Interlayer excitons in MoSe$_2$/WSe$_2$ heterostructures from first-principles},
author = {Roland Gillen and Janina Maultzsch},
journal= {arXiv preprint arXiv:1801.06310},
year = {2018}
}
Comments
8 pages main manuscript, 12 pages supplementary information