Correlated topological flat bands in rhombohedral graphite

Flat bands and nontrivial topological properties are two important topics in condensed matter physics over the past decades. Searching for materials with both flat bands and nontrivial topology is fundamentally important to realize exotic physical properties. In this talk, I will introduce our new progress on the observation of topological flat bands in rhombohedral graphite. In particular, we reveal the existence of surface topological flat bands in rhombohedral graphite, which are topologically protected by bulk helical Dirac nodal lines. Moreover, the surface topological flat bands exhibit correlation effects, which are suggested by the splitting and exotic evolution upon in situ electron doping. Our results suggest rhombohedral graphite as a new platform for bridging the two interesting fields of nontrivial topological physics and flat-band induced electronic instabilities.