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

TL;DR

This study demonstrates that the optical conductivity of graphene on SrTiO₃ is significantly renormalized due to resonant excitonic effects involving Ti 3d orbitals, leading to near transparency in the ultraviolet spectrum.

Contribution

It reveals the role of Ti 3d orbitals in mediating excitonic effects that alter graphene's optical properties, supported by ab initio calculations.

Findings

Graphene on SrTiO₃ becomes almost fully transparent in the UV region.

Resonant excitonic effects involve hybridization of graphene and SrTiO₃ orbitals.

Interactions occur below the bulk SrTiO₃ optical band gap.

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.