Electronic correlation effects in the kagome magnet GdMn6Sn6

The recently discovered kagome magnet R Mn6Sn6 ( 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 Gd Mn6Sn6, which contains Mn kagome lattice with in-plane ferrimagnetism. Typical kagome electronic dispersions are found around the Fermi energy ( EF), i.e., Dirac dispersions, flat bands (FBs), and saddle points. The Dirac dispersions with dz2 orbital characters at EF 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 Gd Mn6Sn6. On the other hand, to match the observed FBs with dxy/dx2−y2 orbital characters around 0.4 eV below EF, 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 EF. 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.