We report the first electronic compressibility measurements of magic-angle twisted bilayer graphene. The evolution of the compressibility with carrier density offers insights into the interaction-driven ground state that have not been accessible in prior transport and tunneling studies. From capacitance measurements, we determine chemical potential as a function of carrier density and find the widths of the energy gaps at fractional filling of the moir\'{e} lattice. In the electron-doped regime, we observe unexpectedly large gaps at quarter- and half-filling and strong electron-hole asymmetry. Moreover, we measure a ∼35meV mini-bandwidth that is much wider than most theoretical estimates. Finally, we explore the field dependence up to the quantum Hall regime and observe significant differences from transport measurements.
@article{arxiv.1903.10492,
title = {Electronic Compressibility of Magic-Angle Graphene Superlattices},
author = {S. L. Tomarken and Y. Cao and A. Demir and K. Watanabe and T. Taniguchi and P. Jarillo-Herrero and R. C. Ashoori},
journal= {arXiv preprint arXiv:1903.10492},
year = {2019}
}