Electronic correlation effects in the kagome magnet GdMn 6 Sn 6

The recently discovered kagome magnet $R{\mathrm{Mn}}_{6}{\mathrm{Sn}}_{6}$ ($R$ = Y and lanthanides) features a variety of magnetic ground states and exhibits topological quantum phases. Here we report on a combined angle-resolved photoemission spectroscopy and first-principles calculations study of the electronic structure in $\mathrm{Gd}{\mathrm{Mn}}_{6}{\mathrm{Sn}}_{6}$, which contains Mn kagome lattice with in-plane ferrimagnetism. Typical kagome electronic dispersions are found around the Fermi energy (${E}_{\mathrm{F}}$), i.e., Dirac dispersions, flat bands (FBs), and saddle points. The Dirac dispersions with ${d}_{z2}$ orbital characters at ${E}_{\mathrm{F}}$ are sensitive to adding onsite Hubbard $U$ on the Mn $3d$ atoms, revealing that electronic correlation effectively modulates the Dirac dispersions of a kagome magnet $\mathrm{Gd}{\mathrm{Mn}}_{6}{\mathrm{Sn}}_{6}$. On the other hand, to match the observed FBs with ${d}_{xy}/{d}_{x2\ensuremath{-}y2}$ orbital characters around 0.4 eV below ${E}_{\mathrm{F}}$, the calculated bands are still needed to be overall renormalized by a factor of about 2 after adding a small $U$ for matching the Dirac dispersions at ${E}_{\mathrm{F}}$. The different electronic correlations, which are directly reflected by the Hubbard $U$ and the renormalization factor, could be associated with the orbital-selective kagome bands at the different binding energies. Our findings could have an instructive significance to tuning the individual kagome feature via the electronic correlations.