Layered Multiple Scattering Approach to Hard X-ray Photoelectron Diffraction: Theory and Application
Abstract
Photoelectron diffraction (PED) is a powerful and essential experimental technique for resolving the structure of surfaces with sub-angstrom resolution. In the high energy regime, researchers in angle-resolved photoemission spectroscopy (ARPES) observe modulating patterns attributed to X-ray-PED (XPD) effects. This is accompanied by other challenges such as low cross-sections, significant photon momentum transfer, and non-negligible phonon scattering. Overall, XPD is not only an advantageous approach but also exhibits unexpected effects. To disentangle these diffraction influences, we present a PED implementation for the SPRKKR package that utilizes multiple scattering theory and a one-step model in the photoemission process. Unlike real-space implementations of the multiple scattering XPD formalism, we propose a k-space implementation based on the layer KKR method. The main advantage of this method is its ability to address a very broad kinetic energy range (20-8000 eV) without convergence problems related to angular momentum and cluster size. Furthermore, the so-called alloy analogy model can be used to simulate XPD at finite temperatures as well as XPD effects observed in soft and hard X-ray ARPES. For practical applications, we have calculated the circular dichroism in angular distributions (CDAD) associated with core-level photoemission of 2p from Si(100) and 3p from Ge(100). Photoelectrons are excited by hard X-rays (6000 eV) with right and left circularly polarized radiation (RCP and LCP, respectively).
Cite
@article{arxiv.2411.09669,
title = {Layered Multiple Scattering Approach to Hard X-ray Photoelectron Diffraction: Theory and Application},
author = {Trung-Phuc Vo and Olena Tkach and Sylvain Tricot and Didier Sebilleau and Jurgen Braun and Aki Pulkkinen and Aimo Winkelmann and Olena Fedchenko and Yaryna Lytvynenko and Dmitry Vasilyev and Hans-Joachim Elmers and Gerd Schonhense and Jan Minar},
journal= {arXiv preprint arXiv:2411.09669},
year = {2025}
}