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<p>Flat bands, electronic states with nearly dispersionless energy-momentum structure, provide fertile ground for unconventional quantum phases. Recent observations of flat bands at the Fermi level in kagome metals open the possibility of unifying topology and correlation-driven heavy-fermion physics. Here we show that topology and heavy-fermion correlations coexist in the layered kagome metal YbCr<sub>6</sub>Ge<sub>6</sub>. At high temperatures, an intrinsic kagome flat band—arising from frustrated hopping on the kagome lattice—dominates the Fermi level. Upon cooling, localized Yb 4<i>f</i>-states hybridize with the topological kagome flat bands, transforming this state into momentum-independent Kondo resonance states across the entire Brillouin zone. Topological analysis of the hybridization gaps reveals filling-tunable weak and strong topological Kondo-insulating regimes, and identifies a topological Dirac–Kondo semimetal. Taken together, these results identify YbCr<sub>6</sub>Ge<sub>6</sub> as a prototype of a topological heavy-fermion system and a platform where geometric frustration, strong correlations, and topology converge, with broad implications for correlated quantum matter.</p>

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Coexisting kagome and heavy fermion flat bands in YbCr6Ge6

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月19日

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  • Hanoh Lee,
  • Churlhi Lyi,
  • Taehee Lee,
  • Hyeonhui Na,
  • Jinyoung Kim,
  • Sangjae Lee,
  • Younsik Kim,
  • Anil Rajapitamahuni,
  • Asish K. Kundu,
  • Elio Vescovo,
  • Byeong-Gyu Park,
  • Changyoung Kim,
  • Charles H. Ahn,
  • Frederick J. Walker,
  • Ji Seop Oh,
  • Bo Gyu Jang,
  • Youngkuk Kim,
  • Byungmin Sohn,
  • Tuson Park

摘要

Flat bands, electronic states with nearly dispersionless energy-momentum structure, provide fertile ground for unconventional quantum phases. Recent observations of flat bands at the Fermi level in kagome metals open the possibility of unifying topology and correlation-driven heavy-fermion physics. Here we show that topology and heavy-fermion correlations coexist in the layered kagome metal YbCr6Ge6. At high temperatures, an intrinsic kagome flat band—arising from frustrated hopping on the kagome lattice—dominates the Fermi level. Upon cooling, localized Yb 4f-states hybridize with the topological kagome flat bands, transforming this state into momentum-independent Kondo resonance states across the entire Brillouin zone. Topological analysis of the hybridization gaps reveals filling-tunable weak and strong topological Kondo-insulating regimes, and identifies a topological Dirac–Kondo semimetal. Taken together, these results identify YbCr6Ge6 as a prototype of a topological heavy-fermion system and a platform where geometric frustration, strong correlations, and topology converge, with broad implications for correlated quantum matter.