Fig. 1: Crystal structure, destructive interference and tight-binding model.
From: Observation of flat bands and Dirac cones in a pyrochlore lattice superconductor
a Crystal structure of CeRu2 shown in the conventional unit cell. b Ru atoms form the pyrochlore lattice, where ai are the lattice translation vectors within the faces of the cube. c Magnetization and d resistivity measurements showing superconductivity at 5.1 K. FC means field cooling and ZFC means zero field cooling. e Brillouin zone (BZ) with the high symmetry points labeled. We define kx, ky and kz here with respect to the (111) surface for the convenience of experimental description. f Four-band tight-binding model of the pyrochlore lattice without considering spin-orbit coupling (SOC), where the flat band is doubly-degenerate. g Tight-binding model including SOC. h Mechanism for 3D destructive interference on the pyrochlore lattice. The sites marked by magenta circles have zero Wannier amplitude and do not produce inter-kagome-plane hopping and hence do not detract from the flatness of the bands. i Density functional theory (DFT) calculations with projection onto different atoms. The black dashed rectangle marks out the Dirac points at the X point of the BZ. j Partial density of states (DOS) of the Ce-f and Ru-d orbitals.
