Probing neutral excitations in a chemically selective way using
Resonant Inelastic soft X-ray Scattering


Giacomo Ghiringhelli


INFM/CNR-COHERENTIA and Dipartimento di Fisica - Politecnico di Milano

piazza Leonardo da Vinci 32 - 20133 Milano Italy



Resonant inelastic x-ray scattering (RIXS) can be effectively used to measure the energy and symmetry of neutral electronic excitations in solids. In the soft x-ray range it is particularly powerful for strongly correlated electron systems based on 3d transition metals, because at the L2,3 edges the excitation and de-excitation processes, upon which RIXS is based, directly involve the 3d states.

The reduced intensity and the instrumental energy resolution usually hinder the detection of very detailed spectral features, but the recent progress in the energy resolving power of our RIXS apparatus has opened new exciting possibilities in the 400-1000 eV range.

We have recently measured the dd excitations in cuprates, manganites, cobaltates and other interesting systems where electronic correlation plays a central role. We present some examples of high resolution RIXS at the L2,3 edges of Cu, Ni, Co, Mn and Ti: the rich spectral features can be straightforwardly interpreted using atomic models (crystal field, cluster, impurity). All the spectra were measured using the AXES spectrometer, permanently installed at the beam line ID08 of the ESRF in Grenoble. The combined resolution ranges from 240 meV at the Ti to 650 meV at the Cu. These promising results have motivated the construction of a new very high resolution RIXS spectrometer, allowing also the k dependence, to be installed soon at the Swiss Light Source.