One Step Model Description of HARPES: Inclusion of Disorder and Temperature Effects

Abstract

Angle integrated as well as angle resolved photoemission in the soft and hard X-ray regime became a very important tool to investigate the bulk properties of various materials. In practise enhanced bulk sensitivity can be achieved by so called threshold photoemission. Increased bulk sensitivity may suggest that LSDA band structure or density of states calculations can be directly compared to the measured spectra. However, various important effects, like matrix elements, the photon momentum or phonon excitations, are this way neglected. Here, we present a generalization of the one-step model that describes the excitation of the photoelectron, its transport to the surface and the escape into the vacuum in a coherent way. First, a short introduction to the main features of the one-step model implementation within the Munich SPR-KKR program package is given. The capability to account for correlation effects and chemical disorder using the LSDA+DMFT (dynamical mean field theory) scheme in combination with the coherent potential approximation (CPA) method will be demonstrated by various examples. Special emphasis is put on the description of phonon-assisted transitions which lead to the so-called XPS-limit in the hard X-ray and/or high temperature regime.