Probing the wave functions of correlated states in magic angle graphene

Abstract

Using scanning probe microscopy and spectroscopy, we explore the spatial symmetry of the electronic wave functions of twisted bilayer graphene at the "magic angle"of 1.1°. This small twist angle leads to a long wavelength moiré unit cell on the order of 13 nm and the appearance of two flat bands. As the twist angle is decreased, correlation effects increase until they are maximized at the magic angle. At this angle, the wave functions at the charge neutrality point show reduced symmetry due to the emergence of a charge ordered state. As the system is doped, the symmetry of the wave functions changes at each commensurate filling of the moiré unit cell pointing to the correlated nature of the spin and valley degeneracy broken states.