Infrared absorption of gate-tuned twisted bilayer graphene

We report an infrared transmission measurement performed on electrically gated twisted bilayer graphene. The optical
absorption spectrum manifests two kinds of inter-van Hove singularity transition peaks as well as interlinear-band absorption
step, consistent with predictions from the electron bands of TBG with Moire structures. The
absorption peaks exhibit gate-dependent changes in peak posisionts and strengths which
demonstyrate a nonrigid band
structure modification created by ion-gel gating through layer-dependent Coulomb screening.