9/16/25 (in-person)Â Prof. Dio Margetis, University of Maryland
Title:Â Â Optical conductivity and edge plasmons in the twisted bilayer graphene
Abstract: This talk focuses on recent progress in understanding implications of the optical conductivity tensor of the twisted bilayer graphene (TBG). This material system has attracted much attention, mainly because of its novel electronic phases. First, I will discuss features of the optical conductivity via the Kubo formulation of linear response theory. This theory, together with symmetry considerations, yields a spatially homogeneous conductivity tensor of a certain form. Second, I will use this tensor form in order to analytically derive the dispersion relation of non-retarded edge plasmons, which are electromagnetic modes confined near edges, for a TBG consisting of two semi-infinite flat conducting sheets. This relation explicitly depends on the chirality of the system. Third, by invoking this result, I will describe a correspondence of the chiral optical plasmon in the TBG to the magnetoplasmon in the single-layer graphene, by introducing an effective magnetic field.Â