Diverse emergent correlated electron phenomena have been
observed
in twisted-graphene layers. Many electronic structure predictions
have been reported exploring this new field, but with few momentum-resolved
electronic structure measurements to test them. We use angle-resolved
photoemission spectroscopy to study the twist-dependent (1° <
θ < 8°) band structure of twisted-bilayer, monolayer-on-bilayer,
and double-bilayer graphene (tDBG). Direct comparison is made between
experiment and theory, using a hybridk·pmodel for interlayer coupling. Quantitative agreement is found across
twist angles, stacking geometries, and back-gate voltages, validating
the models and revealing field-induced gaps in twisted graphenes.
However, for tDBG at θ = 1.5 ± 0.2°, close to the
magic angle θ = 1.3°, a flat band is found near the Fermi
level with measured bandwidthEw= 31
± 5 meV. An analysis of the gap between the flat band and the
next valence band shows deviations between experiment (Δh= 46 ± 5 meV) and theory (Δh= 5 meV),
indicative of lattice relaxation in this regime.