Optical conductivity renormalization of graphene on SrTiO${}_3$ due to resonant excitonic effects mediated by Ti 3\textit{d} orbitals

Abstract

We present evidence of a drastic renormalization of the optical conductivity of graphene on SrTiO${}_3$ resulting in almost full transparency in the ultraviolet region. These findings are attributed to resonant excitonic effects further supported by \emph{ab initio} Bethe-Salpeter equation and density functional theory calculations. The ($\pi$,$\pi$*)-orbitals of graphene and Ti-3\textit{d} $t_{2g}$ orbitals of SrTiO${}_3$ are strongly hybridized and the interactions of electron-hole states residing in those orbitals play dominant role in the graphene optical conductivity. These interactions are present much below the optical band gap of bulk SrTiO${}_3$. These results open a possibility of manipulating interaction strengths in graphene via \textit {d}-orbitals which could be crucial for optical applications.

9 pages, 11 figures, Phys. Rev. B (accepted)

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