ARPES Signatures of Few-Layer Twistronic Graphenes
James E. Nunn, Andrew McEllistrim, Astrid Weston, Aitor García-Ruiz, Matthew D. Watson, Marcin Mucha‐Kruczyński, Céphise Cacho, Roman Gorbachev, Vladimir I. Fal’ko, Neil R. Wilson
Abstract
High Resolution Image Download MS PowerPoint Slide 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 hybrid k · p model 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 bandwidth E w = 31 ± 5 meV. An analysis of the gap between the flat band and the next valence band shows deviations between experiment (Δ h = 46 ± 5 meV) and theory (Δ h = 5 meV), indicative of lattice relaxation in this regime.