Many-body interactions in crystalline solids can be conveniently described in terms of quasiparticles with strongly renormalized masses as compared with those of non-interacting particles. Examples of extreme mass renormalization are on the one hand graphene, where the charge carriers obey the linear dispersion relation of massless Dirac fermions, and on the other hand heavy-fermion materials where the effective electron mass approaches the mass of a proton. Here we show that both extremes, Dirac fermions, like they are found in graphene and extremely heavy quasiparticles characteristic for Kondo materials, may not only coexist in a solid but can also undergo strong mutual interactions. Using the example of EuRh2Si2, we explicitly demonstrate that these interactions can take place at the surface and in the bulk. The presence of the linear dispersion is imposed solely by the crystal symmetry, whereas the existence of heavy quasiparticles is caused by the localized nature of the 4f states.
ARPES data of (a) Si- and (b) Eu-terminated surfaces are shown in a colour representation where yellow (red) denotes the largest photoemission intensity. The data were taken at 120 eV photon energy, that is, sensitive to 4f emissions
Respective computations were performed for a surface covered by (a) Si and (b) Eu atoms. The maroon-shaded area corresponds to the surface-projected bulk band structure, whereas the grey lines are the result of a calculation for a slab…
Local density approximation-derived bulk band structure parallel to the 
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direction for several planes defined by different values of kz.
– direction for several planes defined by different values of kz.
