The importance of inter-site coherences in the X-ray absorption spectra of mixed-valent systems

Department of Physics and Astronomy, University of British Columbia - Vancouver, BC V6T 1Z1, Canada

^a subhra@phas.ubc.ca

Received: 3 November 2010
Accepted: 26 January 2011

Abstract

We study the importance of inter-site coherences and quantum interference effects in the X-ray absorption spectroscopy (XAS) of mixed-valent systems. We demonstrate its importance, first for a simple diatomic mixed-valent molecule to elucidate the physics involved, and finally for mixed-valent Ti oxides, using a model calculation including full spin and orbital multiplicities. Our calculations demonstrate the inefficacy of conventional approaches of describing the XAS from mixed-valent systems as incoherent combinations of XAS from the pure-valent end members, and that multiplets forbidden in the single-site approximation can be effectively reached within a multi-site description. These conclusions play an important role in the interpretation of XAS and resonant X-ray scattering (RXS) in terms of the electronic structure of strongly correlated systems.