Extended Data Fig. 4: Undertwisted and overtwisted bilayer graphene.
From: Cascade of electronic transitions in magic-angle twisted bilayer graphene
a, dI/dV(Vb, Vg) measured at the centre of an AA site for 0.85° (0.3% strain) twisted bilayer graphene (device B; initial tunnelling parameters: Vb = −40 mV, I = 30 pA, 381.7 Hz sinusoidal modulation of Vrms = 1.2 mV). These data do not show the cascade features. b, Same as a but divided by I/Vb. c, dI/dV(Vb, Vg) measured at the centre of an AA site for 1.21° (0.2% strain) twisted bilayer graphene (device A; initial tunnelling parameters: Vb = −100 mV, I = 1.5 nA, 4.121 kHz sinusoidal modulation of Vrms = 0.5 mV). These data do not show the cascade features (except possibly very faintly for negative ν). A dip of unknown origin at EF is visible at all carrier densities. The persistence of this dip disqualifies it from being a superconducting or correlated-insulating gap. This dip is likely to be a Coulomb gap or a tip artefact7. d, Same as c but divided by I/Vb.
