Optical Absorption of Armchair MoS₂ Nanoribbons: Enhanced Correlation Effects in the Reduced Dimension

Abstract

We carry out first-principles calculations of the quasi-particle band structure and optical absorption spectra of H-passivated armchair MoS₂ nanoribbons (AMoS₂NRs) by employing the approach combining the Green’s function perturbation theory (<i>GW</i>) and the Bethe-Salpeter equation (BSE), i.e., <i>GW</i>+BSE. Optical absorption spectra of AMoS₂NRs show the exciton multibands (their binding energies are close to or less than 1 eV) which are much stronger than a single layer of MoS₂. However, they are absent in the spectra by the approach of <i>GW</i> and the random phase approximation (RPA), i.e., <i>GW</i>+RPA. This signifies that the excitonic correlation effects are strongly enhanced in the reduced dimensional structure of MoS₂. We also calculate the exciton wave functions for the few lowest energy excitons, which are found to have non-Frenkel character