Direct observation of Γ moiré bands in twisted bilayer WSe₂

Recent transport experiments revealed a correlated insulating phase and quantum criticality points in twisted transition metal dichalcogenides (TMDs) that were predicted to host flat moire´ mini-bands. Despite these exciting experimental observations and theoretical predictions, no direct measurements of the band structure of twisted TMD are available to date. We report here for the first time on the direct observation of flat band in twisted TMDs investigating 57° twisted bilayer WSe₂ by micro-focused angle-resolved photoemission spectroscopy. We resolve multiple moire´ mini-bands with strongly reduced dispersion and significant mini-gaps. By comparison with effective continuum band structure models, we attribute the origin of the flat states to a moderate moire´ potential of ≈ 50 meV emerging from the stacking of the two semiconducting layers. Our results establish a reference for future theoretical and experimental studies of the moire´ physics in twisted TMDs.