Ab Initio Theory of Photoemission from Graphene

Abstract

Angle-resolved photoemission from monolayer and bilayer graphene is studied based on an ab initio one-step theory. The outgoing photoelectron is represented by the time-reversed low energy electron diffraction (LEED) state Φleed*, which is calculated using a scattering theory formulated in terms of augmented plane waves. A strong enhancement of the emission intensity is found to occur around the scattering resonances. The effect of the photoelectron scattering by the underlying substrate on the polarization dependence of the photocurrent is discussed. The constant initial state spectra I(k||,ℏω) are compared to electron transmission spectra T(E) of graphene, and the spatial structure of the outgoing waves is analyzed. It turns out that the emission intensity variations do not correlate with the structure of the T(E) spectra and are caused by rather subtle interference effects. Earlier experimental observations of the photon energy and polarization dependence of the emission intensity I(k||,ℏω) are well reproduced within the dipole approximation, and the Kohn–Sham eigenstates are found to provide a quite reasonable description of the photoemission final states.

Screening in Graphene: Response to External Static Electric Field and an Image-Potential Problem

“…A similar value was chosen for the crystal border in graphene in the Ref. [48]. We expect that the value of z im obtained here should not be affected significantly by the presence of the substrate once the valence electronic structure of graphene is not modified strongly by the substrate.…”

Organic single crystals of charge-transfer complexes: model systems for the study of donor/acceptor interactions

“…50 Similar dependencies on the photon energy to the photoemission current have been extensively observed in few-layer graphene and has been theorized to be due to electron interference effects from adjacent layers. 51,52 It is remarkable that for identical chemical composition and measurement conditions (excitation energy and intensity, measurement geometry and duration), we see qualitatively different electronic structure between the two polymorphs of DBTTF-TCNQ and probe multiple HOMOs for each polymorph (though weakly for the b-phase). Nevertheless, measuring the electronic structure was easier in the a-phase than the b-phase based on the overall signal to noise ratio.…”

Electron transmission and mean free path in molybdenum disulfide at electron-volt energies

“…Its application to an isolated slab is described in Ref. [18]: In the scattering region the wave function is a linear combination of the eigenfunctions of an auxiliary three-dimensional periodic crystal, which contains the TMD sandwich as part of the unit cell. The Bloch eigenfunctions of the auxiliary crystal are obtained in terms of augmented plane waves (see Refs.…”

“…The Bloch eigenfunctions of the auxiliary crystal are obtained in terms of augmented plane waves (see Refs. [17,18]). Inelastic scattering was taken into account by the optical potential, which increases smoothly with energy as calculated for the similar TMD, tungsten diselenide (WSe 2 ), in Ref.…”