Visualizing many body phases in a partially filled kagome flat band

The kagome lattice with spin-orbit coupling exhibits a topologically non-trivial flat band in which the effect of Coulomb interactions between the localized charge carriers is believed to be strong. Hence, material realizations of the kagome lattice provide a promising platform to search for new quantum phases of matter at the confluence of topology and strong electronic correlations. We previously showed that the kagome metal CoSn exhibits a quasi-two-dimensional flat band whose occupied electronic states are strongly localized in real space [1]. Here, we study the low energy density of states of Co_1-xFe_xSn in which partial flat band fillings are realized by hole-doping with Fe.

We will present results from temperature-dependent scanning tunneling microscopy measurements on Co_1-xFe_xSn. Combining high-resolution spectroscopy with spectroscopic imaging on samples with different doping levels x, we observe a rich sequence of electronic states appearing at the Fermi energy that cannot be explained within a single-particle picture. We will discuss our findings in the context of electron-electron interaction-induced many body states at partial flat band fillings.