Bo Gyu Jang

Abstract 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.

Conflicts of Interest The authors declare no conflicts of interest. Data Availability Statement The data that support the findings of this study are available from the corresponding author upon reasonable request. Supporting Information Filename Description pssr70114-sup-0001-SuppData-S1.pdf963 KB Supplementary Material References 1, , , et al., “Discovery of Intrinsic Ferromagnetism in Two-Dimensional van der Waals Crystals,” Nature 546 (2017): 265–269.

Strong correlation effects caused by Hund's coupling have been actively studied during the past decade. Hund's metal, strongly correlated while far from the Mott insulating limit, was studied as a representative example. However, recently it was revealed that a typical Mott system also exhibits a sign of Hund physics by investigating the kink structure in the spectral function of NiS2−xSex.