Important role of screening the electron-hole exchange interaction for the optical properties of molecules near metal surfaces

Thorsten Deilmann and Kristian Sommer Thygesen
Phys. Rev. B 99, 045133 – Published 18 January 2019

Abstract

Optical experiments on nanostructures such as molecules, one- or two-dimensional materials, are often performed with the nanostructures in close proximity of a substrate or some other polarizable media. In this case, the Bethe-Salpeter equation (BSE) can be used to calculate the optical excitations of the nanostructure by including the effect of the substrate via the screened electron-hole interaction. Here we show, that in such an approach, where the states of the substrate are not explicitly included in the BSE Hamiltonian but only enter through the screened Coulomb interaction, it is important also to screen the electron-hole exchange interaction. For the case of molecules like benzene physisorbed on the metallic Au(111) surface, the screening of the exchange interaction by the substrate redshifts the lowest optical transition by up to 300 meV. Furthermore, the screening of the exchange is essential in order to obtain the correct ordering of the size of quasiparticle and optical energy gap.

  • Figure
  • Figure
  • Received 9 November 2018
  • Revised 21 December 2018

DOI:https://doi.org/10.1103/PhysRevB.99.045133

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Thorsten Deilmann1,* and Kristian Sommer Thygesen1,2

  • 1CAMD, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
  • 2Center for Nanostructured Graphene (CNG), Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark

  • *thorsten.deilmann@wwu.de

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Vol. 99, Iss. 4 — 15 January 2019

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