Eur. Phys. J. Special Topics 169, 227-235 (2009)
https://doi.org/10.1140/epjst/e2009-00997-4

High energy photoelectron spectroscopy of correlated electron systems and recoil effects in photoelectron emission

Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan

Corresponding author: ssmsuga@yahoo.co.jp

Abstract

The bulk sensitivity of the high energy photoelectron spectroscopy (PES) in the soft and hard X-ray regions is gradually recognized to be essential for studying the electronic structures of strongly correlated electron systems with different surface and bulk electronic structures. With increasing hν, the kinetic energy (E_K) of photoelectrons is increased with realizing longer inelastic mean free path. Studies of three-dimensional genuine bulk band dispersions and bulk Fermiology are only possible by the soft X-ray angle resolved PES (ARPES). Examples are given for Nd_{2 - x}Ce_xCuO₄ and CeRu₂X₂(X: Si, Ge). The temperature dependence of the Yb 4f spectra provides useful information on valence fluctuation and Kondo resonance. The applicability of the single impurity Anderson model (SIAM) and its limit is discussed in the examples of Yb_{1 - x}Lu_xAl₃ and YbAl₃. The importance of the bulk sensitivity is also demonstrated by the soft and hard X-ray PES for SmOs₄Sb₁₂. When E_K becomes very large, the nucleus (ion) recoil effects become observable on the core photoelectron emission from light elements. The example is shown for Yb_7/8Lu_1/8B₁₂ and the influence of the recoil effects for the future high energy ARPES is briefly discussed.