Infrared absorptions in gate-tuned twisted bilayer graphene

We show that the infrared transmission spectrum of electrically gated twisted bilayer graphene (TBG) manifests dramatic changes such as the splitting of the interlinear-band absorption step, the shift of the inter-van Hove singularity transition peak, and the emergence of a very strong intravalence (intraconduction) band transition. These anomalous optical behaviors demonstrate that non-rigid band econstruction occurs by the ion-gel gating due to layer-dependent Coulomb screening that is confirmed by our band structure calculations. We discuss the implications of such effect on the superconductivity of TBG , and also on possible applications as electrooptical device.