Single-particle excitation of core states in epitaxial silicene

Abstract

Recent studies of core-level X-ray photoelectron spectroscopy (XPS) spectra of silicene on ZrB${}_2$(0001) were found to be inconsistent with the density of states (DOS) of a planar-like structure that has been proposed as the ground state by density functional theory (DFT). To resolve the discrepancy, a reexamination of the XPS spectra and direct theoretical access of accurate single-particle excitation energies are desired. By analyzing the XPS data using symmetric Voigt functions, different binding energies and its sequence of Si $2p$ orbitals can be assigned from previously reported ones where asymmetric pseudo-Voigt functions are adopted. Theoretically, we have adopted an approach developed very recently, which follows the sophisticated $\Delta$ self-consistent field ($\Delta$SCF) methods, to study the single-particle excitation of core states. In the calculations, each single-particle energy and the renormalized core-hole charge density are calculated straightforwardly via two SCF calculations. By comparing the results, the theoretical core-level absolute binding energies including the splitting due to spin-orbit coupling are in good agreement with the observed high-resolution XPS spectra. The good agreement not only resolves the puzzling discrepancy between experiment and theory (DOS) but also advocates the success of DFT in describing many-body interactions of electrons at the surface.

8 pages, 3 figures, 3 tables

References in corpus (5)

• The electronic properties of graphene
• Delta Self-Consistent Field as a method to obtain potential energy surfaces of excited molecules on surfaces
• Core level binding energies in solids from first-principles
• Calculation of the graphene C 1$\text{s}$ core level binding energy
• Band structure of silicene on the zirconium diboride (0001) thin film surface - convergence of experiment and calculations in the one-Si-atom Brillouin zone