Figure 4: Optical and tunnelling spectra of the PA oligomer.
From: Exciton-dominated optical response of ultra-narrow graphene nanoribbons
(a) Measured RD spectra (open circles) and three-phase model fit (solid lines) of PA oligomers formed by polymerization of the molecular precursors on Au(788) at 200 °C. The RD spectrum of the pristine Au substrate has been subtracted. The bottom panel shows the dielectric function of the simulated RD spectrum obtained by applying the three-phase model. The blue bars indicate the energy position and oscillator strength of the determined optical transitions. (b) Tunnelling spectrum recorded on the oligomer, revealing an electronic band gap ΔSTS of 3.7 eV. (c) Optical absorption spectrum and electronic band structure of the oligomer calculated from first principles within the GW-BSE approach. The spectrum has been obtained using a broadening of 0.5 eV and the same spectral lineshape used for fitting the RDS data (see Methods). (d) Calculated exciton wavefunctions of the first and second excitons for the oligomer: the electron distribution is shown at fixed hole position (black dot).
