The 4f multipole ordering effect on core-level spectroscopies of Ce intermetallics

The 3d transition metal compounds and 4f rare earth compounds show attractive phenomena, such as superconductivity and Kondo effect, due to strong electron correlations among localized 3d and 4f electrons. Especially, multipole ordering of orbital and/or spin in 4f and 5f compounds is attracting much attention these years. For example, CeB$_{\mathrm{6}}$ is known to show antiferro-quadrupolar (AFQ) ordering below 3.2K. X-ray core-level spectroscopy is an efficient technique to investigate the electronic states of strongly correlated systems. Recent years, experimental techniques have been rapidly developing and, especially, the progress in experimental resolution has enabled us to observe fine spectral features, which were not formerly observed. These advantages will enable us to observe spectral fine features related with the multipole ordering. In this study, we discuss multipole ordering effects on X-ray spectra for CeB$_{\mathrm{6}}$, especially paying attention on the polarization dependence. In order to simulate the electronic state of CeB$_{\mathrm{6}}$ with the multipole ordering, we use an impurity Anderson model including a simplified RKKY interaction.