Aleksandrs Terentjevs

arXiv2014

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

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 ($π$,$π$*)-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.

cond-mat.str-el↗

arXiv2012

Optical spectra of solids obtained by time-dependent density-functional theory with the jellium-with-gap model exchange-correlation kernel

Within the framework of ab initio time-dependent density-functional theory (TD-DFT), we propose a static approximation to the exchange-correlation kernel based on the jellium-with-gap model. This kernel accounts for electron-hole interactions and it is able to address both strongly bound excitons and weak excitonic effects. TD-DFT absorption spectra of several bulk materials (both semiconductor and insulators) are reproduced in very good agreement with the experiments and with a low computational cost.

cond-mat.other↗