Infrared spectroscopy of small angle twisted trilayer graphene

As the twist angle in graphene moiré systems approaches the magic angle, the interplay of dispersive Dirac bands and inter-layer hybridization gives rise to narrow-bandwidth electronic bands that become distinct from the remaining band structure. At the magic angle, these bands are nearly flat. Due to electron-electron interactions, the flat bands renormalize substantially, leading to correlated insulating phases at partial fillings. In this work, we investigate these correlated effects in dual-gated twisted trilayer graphene with a twist angle of approximately 1.15°. Utilizing infrared optical spectroscopy, we probe intra-band transitions within the moiré band structure to examine the electron density-dependent correlated gaps, as well as the inter-band collective excitations to the remote bands.