Scanning tunneling microscopy of gated twisted bilayer graphene: Suppression of tunneling density of states due to electronic correlations*

‘Magic’ angle(~1.1°) twisted bilayer graphene(TBG) is predicted to host narrow, non-dispersive electronic bands, where the kinetic energy of electrons becomes much smaller than Coulomb interactions. Recent transport measurements in this system showed insulating behavior and superconductivity around half filling of the bands, key signatures of the strongly correlated electronic systems. But the detailed electronic structure and the many-body properties of this system are still not well-understood. We used scanning tunneling microscopy and spectroscopy to measure gated TBG with angles ranging from 0.9° to 2°. When the twist angle was close to the magic angle, at certain carrier densities, we observed strong suppression of the tunneling density of states at the Fermi level associated with electron-electron interactions. Our results may deepen the understanding of strongly correlated behavior in magic angle TBG.