Evidence for momentum-dependent heavy-fermionic electronic structures: Soft x-ray ARPES for the superconductor CeNi2Ge2 in the normal state

We present clear experimental evidence for the momentum-dependent heavy fermionic electronic structures of the $4f$-based strongly correlated system ${\mathrm{CeNi}}_{2}{\mathrm{Ge}}_{2}$ by soft x-ray angle-resolved photoemission spectroscopy. A comparison between the experimental three-dimensional quasiparticle dispersion of ${\mathrm{LaNi}}_{2}{\mathrm{Ge}}_{2}$ and ${\mathrm{CeNi}}_{2}{\mathrm{Ge}}_{2}$ has revealed that heavy fermionic electronic structures are seen in the region surrounding a specific momentum. Furthermore, the wave vectors between the observed ``heavy spots'' are consistent with a result of neutron scattering reflecting magnetic correlations, which could be a trigger for the superconductivity in ${\mathrm{CeNi}}_{2}{\mathrm{Ge}}_{2}$.