Photoemission study of twisted monolayers and bilayers of WSe2 on graphite substrates

Abstract

Using microfocused angle-resolved photoemission spectroscopy we investigated microstructures containing regions of single-layer (SL) and bilayer (BL) ${\mathrm{WSe}}_{2}$ on graphite substrates at different twist angles between SL ${\mathrm{WSe}}_{2}$ and graphite and within the BL ${\mathrm{WSe}}_{2}$. Fermi level electrons emitted from the graphite are sharply focused near their $K{}_{gr}$ points in the Brillouin zone, and, when passing through the ${\mathrm{WSe}}_{2}$, get diffracted to form band replicas readily observed in experimental Fermi surface maps from twisted SL ${\mathrm{WSe}}_{2}$/graphite. We investigated two twisted BL ${\mathrm{WSe}}_{2}$ at twist angles $\ensuremath{\sim}{28}^{\ensuremath{\circ}}$ and $\ensuremath{\sim}{10}^{\ensuremath{\circ}}$ and found no evidence of hybridization gaps at the interlayer band-crossing points, that could be precursors of the flat bands at smaller twist angles. Similarly, no such gaps were found for SL ${\mathrm{WSe}}_{2}$/graphite. Experimental results are complemented by theoretical density functional theory calculations, which suggest that a formation of hybridization gaps in the ${\mathrm{WSe}}_{2}$/graphene (which approximates the experimental ${\mathrm{WSe}}_{2}$/graphite system) sensitively depends on the ${\mathrm{WSe}}_{2}$ band character at the crossing point with the graphene Dirac band.