Eu L3-edge Resonant Inelastic X-ray Scattering on EuB6

We present the frst Eu L$_{3}$-edge resonant inelastic x-ray scattering (RIXS) spectra on the cubic EuB$_{6}$ using vertical and horizontal scattering geometries. EuB$_{6}$ is an undistorted cubic compound being free from complications like lattice distortion. The valence of Eu is 2$^{+}$ (4$f^{7})$. Electronic states near the Fermi edge are formed by the hybridization of Eu 5$d_{x2-y2 }$and B 2$p$. According to optical spectroscopy studies, a number of excitations exist over a wide energy range up to 40 eV. In particular, optical spectrum below 10 eV consists of a number of narrow strong peaks. These peaks were assigned to 2$p$-5$d$ charge transfer or 4$f$-5$d$ on-site excitations. In the current Eu L$_{3}$-edge RIXS experiment, we found that resonant enhancements occur both near and above the Eu L$_{3}$ absorption peak. In both resonance features, we identify a number of narrow energy loss features and compare those features with the optical spectroscopy spectrum. Interestingly, we observed a drastic dependence on measurement geometry in a resonant enhancement above the Eu L3 absorption peak. We discuss the excitation symmetry based on the geometry dependence. This study demonstrates the utility of the rare-earth L$_{3}$-edge RIXS as a probe of excited states in rare-earth systems.