Evolution of charge modulation in twisted bilayer graphene near the magic angle*

Twisting and stacking two layers of graphene with a twist-angle near "magic angle" flattens the energy band and significantly slows down the movement of charge carriers. The resulting strong electron-electron interactions favors the emergence of novel correlated phases, including a charge ordered stripe phase^[1]. Using STM on magic-angle twisted bilayer graphene with a gate tunable doping dependence, we study the evolution of the band structure with doping and its effect on the charge ordered state. When the flat band is empty or full it produces a pronounced STS spectroscopy peak which corresponds to a peak in the density of states. Bringing the Fermi level within the flat band we observe a correlation induced pseuodogap at the Fermi energy accompanied by a spatial variation of the charge distribution that breaks the C3 symmetry. We will report on the evolution of the charge ordered phase with temperature, magnetic field and on its relation to the pseudogap.

[1] Y. Jiang, X. Lai, K. Watanabe, T. Taniguchi, K. Haule, J. Mao, E.Y. Andrei, Charge order and broken rotational symmetry in magic-angle twisted bilayer graphene, Nature, 573 (2019) 91-95.