Three-dimensional higher-order saddle-point-induced flatbands in Co-based kagome metals

Three-dimensional higher-order saddle-point-induced flatbands in Co-based kagome metals

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Dryer The saddle point (Van Hove singularity) exhibits a divergent density of states in two-dimensional systems, leading to fascinating phenomena such as strong correlations and unconventional superconductivity, yet it is seldom observed in three-dimensional (3D) systems.In this work we find two types of 3D higher-order saddle points (HOSPs) in emerging 3D kagome metals YbCo_{6}Ge_{6} and MgCo_{6}Ge_{6}.Both HOSPs exhibit a singularity in their density of states, which is significantly enhanced compared to the ordinary saddle point.

The HOSP near the Fermi energy generates a flatband extending a large area in the Brillouin zone, potentially amplifying the correlation effect and fostering electronic instabilities.Two types of HOSPs exhibit distinct robustness upon element Ski de fond - Equipement - Batons - Adulte substitution and lattice distortions in these kagome compounds.Our work paves the way for engineering exotic band structures, such as saddle points and flatbands, and exploring interesting phenomena in Co-based kagome materials.