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

Hengxin Tan, Yiyang Jiang, Gregory T. McCandless, Julia Y. Chan, Binghai Yan

Research output: Contribution to journalArticlepeer-review

Abstract

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 YbCo6Ge6 and MgCo6Ge6. 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 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.

Original languageEnglish
Article number043132
JournalPHYSICAL REVIEW RESEARCH
Volume6
Issue number4
DOIs
StatePublished - Nov 2024

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy

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