Infrared magnetospectroscopy of the Dirac cone in twisted trilayer graphene

We investigate inter-Landau-level transitions in the dispersive Dirac bands of symmetric twisted trilayer graphene via infrared magnetospectroscopy, toward understanding the evolution of the reconstruction of the trilayer flat bands as a function of carrier density and interaction effects. We probe the first interband cyclotron resonance transitions, N = 0→1 and N = −1→0, across a range of moiré band fillings. For a given filling ν>0, the resonance vanishes at the magnetic field where the N=+1 LL of the Dirac cone becomes completely filled; for ν<0, when the N=−1 level is emptied. The energy Ecrit of the CR transition just before vanishing gives the Fermi energy at a given filling factor, which we compare to calculations in both a single particle and interacting (Hartree-Fock) picture.