Fig. 1
Formation of the large Fermi surface in a Kondo lattice. a Schematic hybridization model for Yb case: the localized and renormalized level of the 4f hole (dashed red line) hybridizes with a light hole-like conduction band (blue) and forms a heavy-quasiparticle band (purple) right below the Fermi level, EF. The Fermi vector shifts from kF to k′F. The red sun symbol indicates the region of f-d hybridization. b ARPES band map of YbRh2Si2 (compare ref. 9). The Brillouin zone cut corresponds to the black line shown in d. The crystal-field-split Yb 4f bands (highlighted in red) hybridize with a bunch of projected bulk bands (shaded in blue) forming a heavy hole-like quasi-particle band at low temperature and shifting the Fermi vector outwards. c, d Schematic representation of a small and large Fermi surface: due to the formation of the Kondo lattice and the Luttinger theorem, the small hole pocket in c transforms into a large hole pocket in d, which incorporates now the additional 4f hole
