G-band enhancement in ABt Twisted Trilayer Graphene

Twisted bilayer graphene is a new platform for investigating exotic properties such as correlated insulator and superconducting states. In particular, it is known to exhibit a G-band enhancement in Raman experiments, which is closely related to the divergent density of states near the van Hove singularities. However, the Raman signatures of twisted trilayer graphene remain unclear. In this talk I will introduce our recent experimental investigation on this question. We experimentally observed the presence of G-band enhancement in twisted trilayer graphene, which consists of one twisted layer on top of an AB-stacked bilayer (ABt twisted trilayer graphene). We identified two centers of G-band enhancements that are centered around 12.3° and 16°, respectively. They correspond to two pairs of van Hove singularities formed by the anti-crossing between the linearly dispersive bands of the twisted layer and the parabolic bands of the AB-stacked bilayer. We utilized the continuum model to map out the G-band intensity with respect to twist angles in Raman measurements, which properly captures these two enhancement centers.