Flat Γ Moiré Bands in Twisted Bilayer WSe2

The recent observation of correlated phases in transition metal dichalcogenide moiré systems at integer and fractional filling promises new insight into metal-insulator transitions and the unusual states of matter that can emerge near such transitions. Here, we combine real- and momentum-space mapping techniques to study moiré superlattice effects in 57.4° twisted ${\mathrm{WSe}}_2$ (${\mathrm{tWSe}}_2$). Our data reveal a split-off flat band that derives from the monolayer $\mathrm{\Gamma }$ states. Using advanced data analysis, we directly quantify the moiré potential from our data. We further demonstrate that the global valence band maximum in ${\mathrm{tWSe}}_2$ is close in energy to this flat band but derives from the monolayer $K$ states which show weaker superlattice effects. These results constrain theoretical models and open the perspective that $\mathrm{\Gamma }$-valley flat bands might be involved in the correlated physics of twisted ${\mathrm{WSe}}_2$.