Quasi-boson/Cumulant Approach to Multi-electron Excitations and Satellites in X-ray Spectra*

by J. J. Rehr (Univ. of Washington Seattle)

Monday 16 Dec 2013, 11:00 → 12:00 Europe/Stockholm

Nordita West (122:026)

There has been significant recent progress in understanding correlation effects in x-ray absorption (XAS), photoemission (XPS), and related spectroscopies [1]. These experiments probe the excited state properties of a system, and thus can reveal physics beyond the independent particle approximation. For example, excitations such as plasmons are largely responsible for mean-free paths and self-energy shifts, and give rise to satellites in XPS spectra [2]. Unlike GW, the theory also. In XAS, the theory accounts for both intrinsic and extrinsic losses, and explains the energy-dependence of quasi-particle and satellite peaks. We also discuss extensions, e.g., for calculations of charge-transfer satellites and phonon contributions to the electron self-energy. The theory is illustrated with a number of applications [2,4]. excitations can all be treated in terms of spectral function derived from a quasi-boson Here we discuss how such an energy-dependent approximation and cumulant-expansion techniques [3] reproduces satellites from multiple boson excitations *Supported by US DOE Grant DE-FG03-97ER45623 and by the CMCSN. [1] John J. Rehr et al., Comptes Rendus Physique 10,548 (2009). [2] M. Guzzo et al., Phys. Rev. Lett. 107,166401(2011). [3] L. Hedin, J. Phys.: Condens. Matter 11, R489 (1999. [4] J. Söderström et al., Phys. Rev. Lett. 108, 193005 (2012).